What Is SPMB? State Street SPDR Portfolio Mortgage Backed Bond ETF
Last updated July 2026
Short answer
SPMB is State Street SPDR Portfolio Mortgage Backed Bond ETF, an ETF that tracks a US mortgage-backed securities index at a 0.04% expense ratio. SPMB holds US mortgage-backed securities, bundled into one ticker. It distributes about 4.07%, and that payout moves with rates rather than being fixed. It launched in 2009. It charges 0.04%.
SPMB is issued by State Street SPDR and tracks a US mortgage-backed securities index. It charges a 0.04% expense ratio, holds approximately $7.1B in assets under management, yields about 4.07%, and launched in 2009.
What is SPMB?
SPMB is State Street SPDR Portfolio Mortgage Backed Bond ETF, an ETF that tracks a US mortgage-backed securities index at a 0.04% expense ratio. SPMB holds US mortgage-backed securities, bundled into one ticker. It distributes about 4.07%, and that payout moves with rates rather than being fixed. It launched in 2009. It charges 0.04%.
SPMB is issued by State Street SPDR and tracks a US mortgage-backed securities index, so a single ticker gives you the whole portfolio of underlying holdings weighted by the index's methodology rather than by any active stock-picking.
What does SPMB hold?
SPMB is weighted toward its largest constituents. As of August 2026, the top holdings are:
| Rank | Ticker | Company | % of SPMB | |
|---|---|---|---|---|
| 1 | GVMXX | State Street Instl US Govt MMkt Premier | 7.7% |
The remaining holdings make up the balance of the fund, with weights tapering off below the top names. Because the index reconstitutes on a rolling basis, the roster stays current without active management. Each ticker above links to its individual stock guide in Walnut.
How do I invest in SPMB?
There are three common ways to get SPMB exposure. Buy shares (or fractional shares) of SPMB directly at any major broker that lists it. Hold it as a core position and layer more concentrated ideas on top. Or build it into a thematic portfolio in Walnut, so SPMB sits alongside other holdings that express the same thesis, with target weights you can rebalance toward. SPMB trades like a stock during market hours, so you buy it the same way you would any listed share.
New to buying funds? See how to buy an ETF, step by step.
Is SPMB a good buy?
Whether SPMB is a good buy depends less on any single call and more on your time horizon and what you already hold: it tracks a US mortgage-backed securities index, so the real question is whether you want that exposure in your mix and at what weight. We walk through valuation, concentration, and what would have to be true for it to outperform from here in is SPMB a buy?
The bottom line on SPMB
SPMB gives you a US mortgage-backed securities index exposure in one ticker at a 0.04% expense ratio. Most investors use it as a core holding and layer more concentrated thematic portfolios on top.
More on SPMB
Whether SPMB is worth buying today depends more on your time horizon and what you already hold than on any single call. We walk through valuation, concentration, and what would have to be true for it to outperform from here in is SPMB a buy?
SPMB yields 4.07% as of August 2026, paid by passing through the dividends of its underlying holdings. For the payout schedule, history, and how the distributions are taxed, see SPMB dividend: yield and schedule.
New to funds like SPMB? Start with what an ETF is, then how to buy an ETF, or browse the full guide to ETF investing.
Wondering how SPMB fits the portfolio you already own? Walnut is an AI investing app that connects your brokerage read-only and answers questions like that about your actual holdings: overlap, concentration, and how each position tracks the S&P 500. Compare the best AI portfolio analyzers or see the best AI investing apps in 2026.
Investing in SPMB with AI
Connect the broker you already use and ask Walnut's AI how SPMB fits what you actually hold: what it overlaps with, what it leaves you exposed to, and how it has tracked the S&P 500. Read-only by default, and you approve anything before it reaches your broker.
FAQ
What is SPMB's ticker symbol?
+
SPMB, State Street SPDR Portfolio Mortgage Backed Bond ETF. Issued by State Street SPDR; tracks a US mortgage-backed securities index. Trades during US market hours, available at every major US brokerage.
What is SPMB's expense ratio?
+
0.04% as of August 2026.
What are SPMB's top holdings?
+
Top holdings as of August 2026: GVMXX and others. See the full holdings table above.
How can I invest in SPMB through Walnut?
+
Walnut isn't a broker. Connect a brokerage and Walnut sits on top to help you build and track thematic portfolios. SPMB can be a constituent alongside individual stocks.
How do I compare SPMB to similar ETFs?
+
Put a few fields side by side: the expense ratio (fees compound over decades), the index or strategy it tracks, the top holdings and how much they overlap with what you already own, the dividend yield, and the AUM, liquidity, and bid-ask spread that affect trading costs. For index funds, tracking error (how closely it follows its index) and tax efficiency matter too. SPMB's figures are above; the full method is in Walnut's guide on how to compare ETFs.
Related ETFs
Walnut is informational, not investment advice. Holdings weights and fund statistics on this page are approximations stamped to August 2026; verify current figures against State Street SPDR's fund page or your broker before investing.