I examine the timing ability of mutual fund investors in Taiwanese market in individual fund level. From March 2001 to February 2011, the timing ability and the return-chasing behavior of Taiwanese mutual fund investors reduce their average annual return by 1.22%. The underperformance is more observable on funds with investment target in Taiwanese market, with larger net cash flow changes, with purchase load and with more actively managed strategy. But under bear or recovery market, the investors’ return-chasing behaviors make them outperform than the one with passive strategy.