A bond fund is an investment fund that puts most of its money into bonds and other debt securities, such as government and corporate bonds, mortgage-backed securities and short-term notes. Investors own shares of the fund rather than the bonds themselves, receive a share of the interest the portfolio earns, and see the value of their shares rise and fall with bond prices. Bond funds are also called fixed income funds.
Bond funds come as a mutual fund, an exchange-traded fund (ETF) or a closed-end fund. They sit between the money market fund, which holds only very short-term debt, and the equity fund, which holds shares. The key difference from owning a single bond is that a bond fund usually never matures: the manager keeps replacing bonds as they come due, so there is no fixed date on which the investor is promised their money back.
Bond fund in plain terms
Imagine lending small sums to hundreds of borrowers at once, governments and companies alike, and getting a share of all the interest they pay. A bond fund does exactly that on your behalf. Rather than one large IOU that could go wrong, you hold a thin slice of many.
The catch is that the IOUs can be bought and sold, and their price moves with interest rates. When new loans start paying more, older ones paying less become worth less, a bit like last year's phone model losing value when a better one comes out. So the regular income tends to be steady, but the value of your stake can go up and down.
Types of bond fund
- Government bond funds hold Treasury securities and other sovereign or agency debt, with low credit risk.
- Corporate bond funds hold corporate bonds, usually investment-grade bonds rated BBB-/Baa3 or above.
- High-yield funds hold junk bonds, which pay more because their issuers are more likely to default.
- Municipal bond funds hold US state and local government debt whose interest is often tax-exempt income at the federal level.
- International and emerging-market funds add currency and country risk.
- Short-, intermediate- and long-term funds are grouped by the maturity of what they hold, from under about three years to over ten.
Specialist funds hold inflation-linked bonds, green bonds, convertible bonds or Islamic sukuk.
Income, yield and risk
Most bond funds pay income monthly. Many accrue it daily, so a shareholder earns income for each day they hold shares; the per-share amount is the daily dividend factor shown on a fund fact sheet. US funds must quote a standardised 30-day SEC yield, and fact sheets often show the portfolio's average yield to maturity (YTM) as well.
The main risk is interest rate risk. A fund's duration, usually given in years, estimates how much its value changes for a one-percentage-point move in rates: a fund with a duration of 6 would be expected to lose about 6% if rates rose by one point, and gain about 6% if they fell by one point. Funds also report their weighted average maturity, which is related but not the same. The 2022 rate rises showed the risk plainly: the Bloomberg US Aggregate Bond Index lost about 13% that year, its worst calendar year on record. Other risks include credit risk, liquidity risk in stressed markets and, for foreign bonds, currency risk.
Costs and regulation
According to the Investment Company Institute, the asset-weighted average expense ratio of US bond mutual funds was 0.36% in 2025, and of index bond ETFs 0.09%. Because bond returns are usually lower than stock returns, fees take a bigger share of what the investor earns, so cost matters even more here.
In the United States a fund whose name suggests bonds must invest at least 80% of its assets accordingly under the SEC's "Names Rule" (Rule 35d-1), which was widened in 2023 with compliance phased in from June 2026. Bond ETFs and mutual funds fall under the Investment Company Act of 1940; in Europe they are usually UCITS funds.
Bond funds compared with individual bonds
An individual bond held to maturity returns its face value if the issuer does not default, whatever happened to prices along the way. A bond fund has no such end point, so a loss caused by rising rates is only recovered over time as the fund reinvests at the new, higher yields. In exchange, the fund gives diversification across hundreds of issues, professional credit research, easy reinvestment and the ability to sell on any business day. Investors using bonds to balance stock risk, as in a balanced fund, often choose funds for that convenience.