iShares Trust - iShares MBS ETF
US ˙ NasdaqGM ˙ US4642885887

SecurityMBB / iShares Trust - iShares MBS ETF
InstitutionCitadel Advisors Llc
ManagerKen Griffin
Latest Disclosed Ownership127,545 shares
Latest Disclosed Value $ 12,110,398
Citadel Advisors Llc ownership in MBB / iShares Trust - iShares MBS ETF

On May 15, 2026 - Citadel Advisors Llc filed a 13F-HR form disclosing ownership of 127,545 shares of iShares Trust - iShares MBS ETF (US:MBB) valued at $12,110,398 USD as of March 31, 2026. The entity filed a previous 13F-HR on May 15, 2025 disclosing 0 shares of iShares Trust - iShares MBS ETF. The current value of the position is $12,003,260 USD.

Citadel Advisors Llc has a history of taking positions in derivatives of the underlying security (MBB) in the form of stock options. The firm currently holds call options representing 10,100 of underlying shares valued at $958,995 USD and put options representing 4,500 of underlying shares valued at $427,275 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MBB / iShares Trust - iShares MBS ETF Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F ISHARES TR MBS ETF 464288588 127,545 127,545 12,110 0.0017
2025-05-15 2025-03-31 13F ISHARES TR MBS ETF 464288588 0 -266,353 -100.00 0 -100.00
2025-02-14 2024-12-31 13F ISHARES TR MBS ETF 464288588 266,353 161,404 153.79 24,419 142.85 0.0042
2024-11-14 2024-09-30 13F ISHARES TR MBS ETF 464288588 104,949 104,949 10,055 0.0019
2024-05-15 2024-03-31 13F ISHARES TR MBS ETF 464288588 0 -13,766 -100.00 0 -100.00
2024-02-14 2023-12-31 13F ISHARES TR MBS ETF 464288588 13,766 -244,284 -94.67 1,295 -94.35 0.0003
2023-11-14 2023-09-30 13F ISHARES TR MBS ETF 464288588 258,050 89,421 53.03 22,915 45.70 0.0049
2023-08-14 2023-06-30 13F ISHARES TR MBS ETF 464288588 168,629 162,191 2,519.28 15,727 2,482.43 0.0033
2023-05-15 2023-03-31 13F ISHARES TR MBS ETF 464288588 6,438 4,467 226.64 610 234.62 0.0001
2023-02-14 2022-12-31 13F ISHARES TR MBS ETF 464288588 1,971 -27,494 -93.31 183 -93.25 0.0000
2022-11-14 2022-09-30 13F ISHARES TR MBS ETF 464288588 29,465 29,465 2,698 0.0006
2022-08-15 2022-06-30 13F ISHARES TR MBS ETF 464288588 0 -19,653 -100.00 0 -100.00
2022-05-16 2022-03-31 13F ISHARES TR MBS ETF 464288588 19,653 -822,651 -97.67 2,002 -97.79 0.0004
2022-02-14 2021-12-31 13F ISHARES TR MBS ETF 464288588 842,304 842,304 90,489 0.0185
2022-03-11 2021-09-30 13F/A-1 ISHARES TR MBS ETF 464288588 0 -882,872 -100.00 0 -100.00
2021-11-15 2021-09-30 13F ISHARES TR MBS ETF 464288588 0 -882,872 0
2021-08-16 2021-06-30 13F ISHARES TR MBS ETF 464288588 882,872 -4,251,299 -82.80 95,553 -82.83 0.0214
2021-05-21 2021-03-31 13F/A-1 ISHARES TR MBS ETF 464288588 5,134,171 4,492,215 699.77 556,647 687.35 0.1366
2021-05-17 2021-03-31 13F ISHARES TR MBS ETF 464288588 5,134,171 4,492,215 556,647 0.1366
2021-02-16 2020-12-31 13F ISHARES TR MBS ETF 464288588 641,956 641,956 -87.50 70,699 -87.30 0.0184
2020-11-16 2020-09-30 13F ISHARES TR Cmn 464288588 0 -9,016 -100.00 0 -100.00
2020-08-14 2020-06-30 13F ISHARES TR Cmn 464288588 9,016 -162,673 -94.75 998 -94.74 0.0004
2020-05-15 2020-03-31 13F ISHARES TR Cmn 464288588 171,689 163,510 1,999.14 18,961 2,044.91 0.0085
2020-02-14 2019-12-31 13F ISHARES TR Cmn 464288588 8,179 8,179 -95.24 884 -95.34 0.0004
2019-05-15 2019-03-31 13F ISHARES TR Cmn 464288588 0 -13,612 -100.00 0 -100.00
2019-02-14 2018-12-31 13F ISHARES TR Cmn 464288588 13,612 -2,684 -16.47 1,424 -15.44 0.0008
2018-11-13 2018-09-30 13F ISHARES TR Cmn 464288588 16,296 16,296 19.72 1,684 18.26 0.0008
2018-08-14 2018-06-30 13F/A-1 ISHARES TR Cmn 464288588 0 -4,044 -100.00 0 -100.00
2018-05-14 2018-03-31 13F/A-1 ISHARES TR Cmn 464288588 4,044 901 28.67 423 26.27 0.0002
2018-05-11 2018-03-31 13F ISHARES TR Cmn 464288588 4,044 901 423
2017-05-12 2017-03-31 13F ISHARES TR Cmn 464288588 3,143 -8,343 -72.64 335 -72.56 0.0003
2017-02-10 2016-12-31 13F ISHARES TR Cmn 464288588 11,486 11,486 265.45 1,221 264.48 0.0012
2014-08-14 2014-06-30 13F ISHARES MBS ETF Cmn 464288588 0 -11,372 -100.00 0 -100.00
2015-06-26 2014-03-31 13F/A-3 ISHARES MBS ETF Cmn 464288588 11,372 11,372 1,207 0.0095
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F ISHARES TR MBS ETF Call 10,100 959 n/a n/a n/a
2026-02-17 2025-12-31 13F ISHARES TR MBS ETF Call 0 -100.00 0 n/a n/a n/a
2025-11-14 2025-09-30 13F ISHARES TR MBS ETF Call 77,600 1.44 7,384 2.80 n/a n/a n/a
2025-08-14 2025-06-30 13F ISHARES TR MBS ETF Call 76,500 2.00 7,183 2.12 n/a n/a n/a
2025-05-15 2025-03-31 13F ISHARES TR MBS ETF Call 75,000 -10.71 7,034 -8.67 n/a n/a n/a
2025-02-14 2024-12-31 13F ISHARES TR MBS ETF Call 84,000 -5.19 7,701 -9.27 n/a n/a n/a
2024-11-14 2024-09-30 13F ISHARES TR MBS ETF Call 88,600 -39.40 8,489 -36.76 n/a n/a n/a
2024-08-14 2024-06-30 13F ISHARES TR MBS ETF Call 146,200 15.12 13,423 14.36 n/a n/a n/a
2024-05-15 2024-03-31 13F ISHARES TR MBS ETF Call 127,000 -7.37 11,737 -9.00 n/a n/a n/a
2024-02-14 2023-12-31 13F ISHARES TR MBS ETF Call 137,100 92.56 12,898 104.02 n/a n/a n/a
2023-11-14 2023-09-30 13F ISHARES TR MBS ETF Call 71,200 30.88 6,323 24.62 n/a n/a n/a
2023-08-14 2023-06-30 13F ISHARES TR MBS ETF Call 54,400 -11.26 5,074 -12.62 n/a n/a n/a
2023-05-15 2023-03-31 13F ISHARES TR MBS ETF Call 61,300 70.28 5,807 73.88 n/a n/a n/a
2023-02-14 2022-12-31 13F ISHARES TR MBS ETF Call 36,000 42.86 3,339 44.67 n/a n/a n/a
2022-11-14 2022-09-30 13F ISHARES TR MBS ETF Call 25,200 -29.61 2,308 -33.87 n/a n/a n/a
2022-08-15 2022-06-30 13F ISHARES TR MBS ETF Call 35,800 -63.91 3,490 -65.47 n/a n/a n/a
2022-05-16 2022-03-31 13F ISHARES TR MBS ETF Call 99,200 10,106 n/a n/a n/a
2022-03-11 2021-09-30 13F/A ISHARES TR MBS ETF Call 0 -100.00 0 -100.00 n/a n/a n/a
2021-11-15 2021-09-30 13F ISHARES TR MBS ETF Call 0 0 n/a n/a n/a
2021-08-16 2021-06-30 13F ISHARES TR MBS ETF Call 4,500 -48.28 487 -48.36 n/a n/a n/a
2021-05-21 2021-03-31 13F/A ISHARES TR MBS ETF Call 8,700 -30.40 943 -31.52 n/a n/a n/a
2021-05-17 2021-03-31 13F ISHARES TR MBS ETF Call 8,700 943 n/a n/a n/a
2021-02-16 2020-12-31 13F ISHARES TR MBS ETF Call 12,500 -58.19 1,377 -58.29 n/a n/a n/a
2020-11-16 2020-09-30 13F ISHARES TR MBS ETF Call 29,900 247.67 3,301 246.74 n/a n/a n/a
2020-08-14 2020-06-30 13F ISHARES TR Cmn Call 8,600 -55.90 952 -55.80 n/a n/a n/a
2020-05-15 2020-03-31 13F ISHARES TR Cmn Call 19,500 126.74 2,154 126.26 n/a n/a n/a
2020-02-14 2019-12-31 13F ISHARES TR Cmn Call 0 -100.00 0 -100.00 n/a n/a n/a
2019-11-14 2019-09-30 13F ISHARES TR Cmn Call 5,000 542 n/a n/a n/a
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-15 2026-03-31 13F ISHARES TR MBS ETF Put 4,500 -77.72 427 -77.80 n/a n/a n/a
2026-02-17 2025-12-31 13F ISHARES TR MBS ETF Put 20,200 102.00 1,923 102.21 n/a n/a n/a
2025-11-14 2025-09-30 13F ISHARES TR MBS ETF Put 10,000 66.67 952 68.92 n/a n/a n/a
2025-08-14 2025-06-30 13F ISHARES TR MBS ETF Put 6,000 3.45 563 3.68 n/a n/a n/a
2025-05-15 2025-03-31 13F ISHARES TR MBS ETF Put 5,800 -72.25 544 -71.66 n/a n/a n/a
2025-02-14 2024-12-31 13F ISHARES TR MBS ETF Put 20,900 -25.89 1,916 -29.06 n/a n/a n/a
2024-11-14 2024-09-30 13F ISHARES TR MBS ETF Put 28,200 -38.29 2,702 -35.61 n/a n/a n/a
2024-08-14 2024-06-30 13F ISHARES TR MBS ETF Put 45,700 -11.95 4,196 -12.53 n/a n/a n/a
2024-05-15 2024-03-31 13F ISHARES TR MBS ETF Put 51,900 -70.54 4,797 -71.07 n/a n/a n/a
2024-02-14 2023-12-31 13F ISHARES TR MBS ETF Put 176,200 -11.50 16,577 -6.24 n/a n/a n/a
2023-11-14 2023-09-30 13F ISHARES TR MBS ETF Put 199,100 1.01 17,680 -3.82 n/a n/a n/a
2023-08-14 2023-06-30 13F ISHARES TR MBS ETF Put 197,100 314.95 18,383 308.58 n/a n/a n/a
2023-05-15 2023-03-31 13F ISHARES TR MBS ETF Put 47,500 -55.32 4,500 -54.37 n/a n/a n/a
2023-02-14 2022-12-31 13F ISHARES TR MBS ETF Put 106,300 96.13 9,859 98.61 n/a n/a n/a
2022-11-14 2022-09-30 13F ISHARES TR MBS ETF Put 54,200 9.49 4,964 2.86 n/a n/a n/a
2022-08-15 2022-06-30 13F ISHARES TR MBS ETF Put 49,500 8.08 4,826 3.43 n/a n/a n/a
2022-05-16 2022-03-31 13F ISHARES TR MBS ETF Put 45,800 573.53 4,666 538.30 n/a n/a n/a
2022-02-14 2021-12-31 13F ISHARES TR MBS ETF Put 6,800 240.00 731 238.43 n/a n/a n/a
2021-11-15 2021-09-30 13F ISHARES TR Cmn Put 2,000 -97.95 216 -97.95 n/a n/a n/a
2021-08-16 2021-06-30 13F ISHARES TR MBS ETF Put 97,400 144.72 10,542 144.31 n/a n/a n/a
2021-05-21 2021-03-31 13F/A ISHARES TR MBS ETF Put 39,800 30.07 4,315 28.04 n/a n/a n/a
2021-05-17 2021-03-31 13F ISHARES TR MBS ETF Put 39,800 4,315 n/a n/a n/a
2021-02-16 2020-12-31 13F ISHARES TR MBS ETF Put 30,600 -71.88 3,370 -71.94 n/a n/a n/a
2020-11-16 2020-09-30 13F ISHARES TR MBS ETF Put 108,800 58.83 12,012 58.41 n/a n/a n/a
2020-08-14 2020-06-30 13F ISHARES TR Cmn Put 68,500 838.36 7,583 840.82 n/a n/a n/a
2020-05-15 2020-03-31 13F ISHARES TR Cmn Put 7,300 0.00 806 2.15 n/a n/a n/a
2020-02-14 2019-12-31 13F ISHARES TR Cmn Put 7,300 -28.43 789 -28.60 n/a n/a n/a
2019-11-14 2019-09-30 13F ISHARES TR Cmn Put 10,200 43.66 1,105 44.63 n/a n/a n/a
2019-08-14 2019-06-30 13F ISHARES TR Cmn Put 7,100 -30.39 764 -30.86 n/a n/a n/a
2019-05-15 2019-03-31 13F ISHARES TR Cmn Put 0 -100.00 0 -100.00 n/a n/a n/a
2019-02-14 2018-12-31 13F ISHARES TR Cmn Put 4,000 419 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.