It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term retirement investors' portfolios.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

If you are looking to diversify your portfolio, consider Harbor Capital Appreciation Institutional (HACAX Quick QuoteHACAX - Free Report) . HACAX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. This fund is a winner, boasting an expense ratio of 0.67%, management fee of 0.6%, and a five-year annualized return track record of 17.91%.

PGIM Jennison Small Company Z (PSCZX Quick QuotePSCZX - Free Report) . Expense ratio: 0.81%. Management fee: 0.67%. PSCZX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. This fund has managed to produce a robust 14.34% over the last five years.

John Hancock Discipline Value Mid Cap R2 (JVMSX Quick QuoteJVMSX - Free Report) : 1.25% expense ratio and 0.71% management fee. JVMSX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. With a five-year annual return of 13.23%, this fund is a well-diversified fund with a long track record of success.

There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk.