OBJECTIVE: Near-misses are a structural characteristic of gambling products that can be engineered within modern digital games. Over a series of preregistered experiments using an online slot machine simulation, we investigated the impact of near-miss outcomes on subjective ratings (motivation, valence) and two behavioral measures (speed of gambling, bet size). METHOD: = 172) measured bet size as a function of the previous trial outcome. RESULTS: In Study 1a, near-misses increased the motivation to continue gambling relative to full-misses, supporting Hypothesis 1. On valence ratings, near-misses were rated significantly more positively than full-misses, in the opposite direction to Hypothesis 2; this effect was confirmed in a close replication (Study 1b). In Study 2, participants gambled faster following near-misses relative to full-misses, supporting Hypothesis 3. In Study 3, participants significantly increased their bet size following near-misses relative to full-misses, supporting Hypothesis 4. CONCLUSION: Across all dependent variables, near-miss outcomes yielded statistically significant differences from objectively equivalent full-miss outcomes, corroborating the "near-miss effect" across both subjective and behavioral measures, and in the environment of online gambling. The unexpected findings on valence ratings are considered in terms of boundary conditions for the near-miss effect, and competing theoretical accounts based on frustration/regret, goal generalization, and skill acquisition. (PsycInfo Database Record (c) 2024 APA, all rights reserved).