Gambling warning messages have been shown to lead to prevention and modification of risk-taking behaviors. Laboratory studies have shown messages can increase a player's knowledge about gambling specific risks, modify their gambling-related cognitive distortions, and even change play. In the present laboratory study, participants were randomly assigned to a winning or losing slot machine gambling experience where they either viewed periodic warning messages or not. It was hypothesized that those in the message conditions would place smaller bets, spend more time considering bets, and spend less time gambling than those in the control conditions. We also hypothesized participants would play differently across the contexts of winning or losing. The results showed those who received warning messages while winning made the fewest number of spins and did not speed up their bet rate over the course of play as much as those in other conditions. Players who received warning messages while losing decreased the size of their bets over the course of play compared to those who received messages while winning. Despite receiving warning messages, losing players did not decrease their number of spins or rate of betting. Winning or losing during slot machine play appears to have significant consequences on the impact of a warning message. Whereas a message to change gambling behavior may encourage a winning gambler to stop play, the same message for a losing player may lead to a small minimization in harm by helping them to decrease bet size, though not their rate of betting.