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 Cambiar SMID Fund Investor (CAMMX Quick QuoteCAMMX - Free Report) . CAMMX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. This fund is a winner, boasting an expense ratio of 0.92%, management fee of 0.8%, and a five-year annualized return track record of 11.24%.

Deutsche Science and Technology Institutional (KTCIX Quick QuoteKTCIX - Free Report) : 0.69% expense ratio and 0.45% management fee. KTCIX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. KTCIX, with annual returns of 10.33% over the last five years, is a well-diversified fund with a long track record of success.

Congress Large Cap Growth Fund (CAMLX Quick QuoteCAMLX - Free Report) : 0.94% expense ratio and 0.5% management fee. CAMLX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With a five-year annual return of 10.35%, 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.