This study is the first to compare the accuracy of self-reported with actual monetary outcomes of online fixed odds sports betting, live action sports betting, and online casino gambling at the individual level of analysis. Subscribers to bwin.party digital entertainment's online gambling service volunteered to respond to the Brief Bio-Social Gambling Screen and questions about their estimated gambling results on specific games for the last 3 or 12 months. We compared the estimated results of each subscriber with his or her actual betting results data. On average, between 34% and 40% of the participants expressed a favorable distortion of their gambling outcomes (i.e., they underestimated losses or overestimated gains) depending on the time period and game. The size of the discrepancy between actual and self-reported results was consistently associated with the self-reported presence of gambling-related problems. However, the specific direction of the reported discrepancy (i.e., favorable vs. unfavorable bias) was not associated with gambling-related problems.