Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

Thornburg Investment Income Builder R5 (TIBMX): 0.99% expense ratio and 0.69% management fee. TIBMX is a part of the Allocation Balanced fund category; these funds like to invest in a variety of asset types, finding a balance between stocks, bonds, cash, and sometimes even precious metals and commodities; they are mostly categorized by their respective asset allocation. TIBMX has achieved five-year annual returns of an astounding 13.69%.

Invesco Technology Fund R5 (FTPIX): 0.72% expense ratio and 0.6% management fee. FTPIX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. With yearly returns of 10.36% over the last five years, FTPIX is an effectively diversified fund with a long reputation of solidly positive performance.

FullerThaler Behav SmallCap Ins (FTHSX Quick QuoteFTHSX - Free Report) : 0.76% expense ratio and 0.6% management fee. FTHSX is a Small Cap Blend mutual fund, allowing investors a way to diversify their funds among various types of small-cap stocks. With a five-year annual return of 10.17%, this fund is a well-diversified fund with a long track record of success.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.