There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

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 learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Fidelity Advisor Series Equity Growth

(FMFMX Quick QuoteFMFMX - Free Report) : 0.01% expense ratio and 0% management fee. FMFMX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. FMFMX has achieved five-year annual returns of an astounding 20.09%.

Principal Capital Appreciation I

(PWCIX Quick QuotePWCIX - Free Report) : 0.45% expense ratio and 0.43% management fee. PWCIX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. PWCIX, with annual returns of 15.3% over the last five years, is a well-diversified fund with a long track record of success.

PGIM Jennison International Opportunity Z

(PWJZX Quick QuotePWJZX - Free Report) : 0.9% expense ratio and 0.81% management fee. PWJZX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. With a five-year annual return of 9.81%, 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.