Sports betting is expanding globally through introduction into new markets and growth in existing markets. Traditionally, bets were placed on the outcome of a match before match commencement, with the outcome not determined for hours or even days. The advent of in-play betting has reduced the delay between bet and outcome. A controversial form of in-play betting is betting on micro events (micro-betting), where consumers bet on outcomes such as the next ball in cricket, or the next point in tennis, with the outcome determined almost immediately. This enables rapid, impulsive and continuous betting and may heighten the risk of problem gambling. We surveyed 1813 Australian sports bettors to determine demographic, behavioural and psychological characteristics of micro event bettors, and of those who place a higher proportion of their bets on micro events. Our two hypotheses were supported: that more highly engaged bettors, including those with gambling problems, are more likely to (1) bet on micro events, and (2) place more of their bets on micro events. Of those who bet on micro events, 78% met criteria for problem gambling, and only 5% non-problem gambling (vs 29% and 28% respectively for non micro event bettors). Placing a higher proportion of bets on micro events was also related to problem gambling. Micro event bettors were likely to: be younger, well educated and single; engaged in a wider variety of gambling activities; and to have high trait impulsivity. Micro event betting appears to appeal almost exclusively to bettors with gambling problems, so a ban would represent a highly targeted intervention to reduce gambling-related harm.