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.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Fidelity Convertible Securities (FCVSX Quick QuoteFCVSX - Free Report) : 0.73% expense ratio and 0.51% management fee. FCVSX is a Convertible Bonds mutual fund, and these funds are unique in the fixed income world; these securities have components of both fixed income and equity, making them hybrid securities. FCVSX has achieved five-year annual returns of an astounding 11.77%.

JHancock Strategic Growth I (JSGIX Quick QuoteJSGIX - Free Report) : 0.73% expense ratio and 0.55% management fee. JSGIX 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. JSGIX, with annual returns of 11.22% over the last five years, is a well-diversified fund with a long track record of success.

Neuberger Berman Small Cap Growth Adviser (NBMVX Quick QuoteNBMVX - Free Report) . Expense ratio: 1.4%. Management fee: 1.23%. Five year annual return: 11.74%. NBMVX is one of many Small Cap Growth mutual funds; these funds tend to create their portfolios around stocks with market capitalization of less than $2 billion.

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.