We analyze the role that direct professional experience plays in mutual fund managers' portfolio decisions. In analyzing fund manager career histories hand-collected from their CVs, we find that mutual funds tend to hold more stocks of firms with which their fund managers have prior professional experience in the form of working for sell-side analysts, audit firms, and underwriters in capacities where they can learn about companies that may belong to their portfolios when they later become fund managers. Cross-sectional results reveal that the impact of this professional experience on fund stockholdings intensifies: when the firm has poorer audit quality, has more opaque financial reporting, participates in more related-party transactions, has lower stock liquidity, has poorer corporate governance, is not listed on an overseas stock exchange, and is located in a lax investor protection region; and when the work experience is less distant and lasts for longer. Additionally, we observe that fund managers trade on stocks of firms for which they have relevant professional experience prior to upcoming earnings news. Such trading generates superior returns to their funds and potentially boosts fund managers' own compensation. We further show that corporate site visits serve as a mechanism through which these fund managers acquire firm-specific information. Finally, we document empirical patterns consistent with both knowledge acquisition and professional connections from prior professional experience contributing to our findings.