Best ETFs for a 401(k)

A 401(k) is an employer-sponsored, tax-deferred retirement account: contributions come out of your paycheck before income tax, the money grows untaxed, and you pay tax on withdrawals in retirement. Many employers also match a portion of what you put in, which is additional money on top of your own contribution. Those two features, the match and the tax deferral, are the reason the 401(k) is often the first account people fund.

The constraint is the menu. Unlike a regular brokerage account, where you can buy any ETF, a 401(k) only lets you invest in the funds your plan administrator and employer chose. That list is commonly a dozen or two index mutual funds (an S&P 500 fund, a total international fund, a bond fund, and so on) plus a series of target-date funds. ETFs are rarely on the core menu. The exception is a self-directed brokerage window, an optional feature some plans add that opens a brokerage account inside the 401(k) so you can buy ETFs and individual stocks. So the real question is less “which ETF” and more “which role on my menu does the job that ETF would do.”

Whatever the exact fund names on your menu, the same few roles tend to be available, and each maps cleanly to a familiar ETF. The US core is an S&P 500 index fund, the menu version of VOO, holding the roughly 500 largest US companies; or a total US stock market index fund, the version of VTI, which adds the mid- and small-cap tail. International exposure comes from a total international index fund, the version of VXUS, covering developed and emerging markets outside the US.

The other key role is bonds. A total bond market index fund is the menu version of BND, and it is commonly used to lower a portfolio's overall volatility rather than to maximize return. Finally, most plans list a series of target-date funds (for example a Target 2055 or Target 2060), each an all-in-one holding that bundles US stocks, international stocks, and bonds in a single ticker. Spotting these roles on your menu matters more than the specific fund brand, because the providers (Fidelity, Vanguard, Schwab, and others) sell near-identical index funds for each one.

A widely used structure is the three-fund portfolio adapted to your menu: a US stock index fund as the core, a total international fund, and a total bond fund. The mix between them is set by how far you are from needing the money. Someone decades from retirement often weights heavily toward stocks (US plus international) with a small bond slice; as retirement approaches, the bond slice typically grows to dampen volatility. This is the same logic a target-date fund automates, just done by hand.

The point of keeping it to three roles is that they cover the whole market without overlapping. Holding several US stock funds at once does not diversify; it stacks the same large companies. For a fuller walkthrough of how the pieces fit and rebalance, see our best ETFs for a 3-fund portfolio guide, which uses the brokerage ETF versions of these same building blocks.

A target-date fund is the hands-off option: one fund that holds US stocks, international stocks, and bonds, and shifts gradually toward bonds as its target year nears. That automatic glide path is why a single target-date fund is a complete portfolio on its own, and why it is the default in most 401(k) plans. The trade-off is control. You accept the provider's chosen stock-to-bond split and international weighting rather than setting your own.

Building your own with the three index funds gives you that control and can shave fees, since some target-date funds cost a touch more than the underlying index funds. The cost is effort: you pick the split and rebalance it yourself over time. Both approaches are common and reasonable. A target-date fund favors simplicity; a three-fund mix favors control. Neither is strictly better, and the fee gap has narrowed as target-date funds have gotten cheaper.

A self-directed brokerage window changes the math, because it lets you step outside the menu and buy actual ETFs and stocks inside the 401(k). If yours offers one, you can use the same low-cost ETFs you would use in any taxable or IRA account: VOO or VTI for the US core, VXUS for international, BND for bonds, or a single global fund like VT if you prefer one ticker. Income-focused investors sometimes add a dividend fund like SCHD, though dividends are less of a draw inside a tax-deferred account.

Two caveats. Brokerage windows are optional and many plans do not offer one, so check your plan documents first. And some charge an extra account or trading fee, so it is worth confirming the cost before moving money into the window. When a window is available, it makes the 401(k) behave much more like a regular brokerage account for ETF selection.

Fund names on your menu vary by provider, but the roles are consistent, and each maps to a familiar ETF as of early 2026. If your plan offers a brokerage window, you can buy the ETF versions in the right column directly; otherwise, look for the index mutual fund in the middle column that fills the same role. For the broader retirement picture across account types, see our best ETFs for retirement guide, and for the full category map, the best ETF in every category roundup.

A 401(k) rarely lives in isolation. Many people also have an IRA, a taxable brokerage account, and maybe an old 401(k) from a former job, and the hard part is seeing how those pieces fit together. If your 401(k) holds an S&P 500 index fund and your brokerage holds VOO, you are doubling up on the same large-cap US companies, and that overlap is easy to miss when each account is a separate login.

That is where Walnut fits. It connects your existing brokerage accounts through SnapTrade and lets you ask, in plain language through Claude, ChatGPT, or a built-in assistant, how your whole picture lines up, including how much a 401(k) holding overlaps with what you own elsewhere and how each position is doing against the S&P 500. It is read-only by default, and you approve any trade. Walnut is not an investment adviser; it helps you see and act on your own portfolio rather than telling you what to buy.

The honest answer to “best ETFs for a 401(k)” is that most 401(k) plans do not let you buy ETFs directly. You pick from a menu, usually index mutual funds, so the move is to match the roles to the ETFs they mirror: an S&P 500 or total US fund as the core (the VOO or VTIequivalent), a total international fund (the VXUS equivalent), and a total bond fund (the BND equivalent), or a single target-date fund as an all-in-one. The match and tax-deferral are why the 401(k) is often funded first.

If your plan has a brokerage window, you can buy the same low-cost ETFs, including a single global fund like VT, that you would use anywhere else. Across accounts, the things that matter most are keeping the roles few and non-overlapping and watching fees, which compound over decades. Fund names, expense ratios, and plan features change; treat the specifics here as a starting point and confirm the details in your own plan documents before deciding.