Using unique Australian investment app data, we document gamblers' propensity and sensitivity to spend money on online sports betting upon experiencing mutual fund investment gains. Employing past asset weights within portfolios as instruments for current positions, we find that investment gains lead to more gambling for individuals who previously gambled, suggesting a complementary relationship. We propose that changes in risk attitude resulting from mutual fund investment experiences drive this increased gambling consumption. This tendency, however, hinders the growth of investment wealth, particularly among financially vulnerable individuals. Our study highlights the intricate connection between investment and gambling consumption.