Cognitive biases strongly influence risky decisions with payoffs. Financial risk-taking tends to increase following prior gains, as if gambling with “house money”. Intelligence and personality also influence risk preferences, but the extent to which they moderate susceptibility to cognitive biases is not understood. We evaluated the house money effect and its moderators by combining data from an online horse betting dataset, comprehensive administrative population registry, and intelligence and personality trait measures (N = 11,220). Gains on the previous betting day were associated with increased betting amounts on the following betting day and shorter time between two consequent sessions. This effect was stronger among individuals with higher extraversion, lower conscientiousness, and lower IQ. Intelligence and personality have tangible monetary implications in real-life risky choices.