We study retail investor trading around institutional investment disclosures by Berkshire Hathaway. Using 13F filings from 2007 to 2023, we examine whether retail investors mimic Berkshire Hathaway’s portfolio adjustments and whether such behaviour affects subsequent returns. We find that retail investors actively engage in institutional copy trading. Stocks associated with Berkshire Hathaway’s new holdings and buy disclosures earn positive abnormal returns for up to 15 days following disclosure, with stronger effects for new positions, but these gains subsequently reverse. In contrast, sell and exit disclosures trigger weaker reactions, consistent with constraints on retail investors’ ability to sell. Taken together, the return dynamics indicate that imitation of a highly visible institutional investor generates short run gains but does not lead to persistent outperformance. Our results contribute to the literature on retail trading, disclosure effects, and copy trading by providing evidence on how retail investors process and respond to institutional portfolio disclosures.