The investigation of rational emotive behaviour therapy (REBT) in sport settings is growing, but controlled experimental field studies are sparse. In the limited extant literature, researchers have found that irrational (extreme, rigid, and illogical) self-talk leads to disrupted motor skill performance, compared to rational (non-extreme, flexible, and logical) self-talk. However, methodological limitations of past research and the absence of sport-relevant tasks limit the application of findings to athletic settings. Therefore, the current study examined the effects of rational and irrational self-talk on the pressured putting performance of amateur golfers, by adopting a controlled and field-based experimental study design. A two-way repeated-measures ANCOVA, controlling for baseline putting ability, revealed that golfers' putting accuracy was significantly better when using rational self-talk than when using irrational self-talk. In addition, one-samples and paired-samples t-tests showed that golfers reported that rational self-talk was more usable than the irrational self-talk, and perceived the rational self-talk to be more facilitative than the irrational self-talk for their putting performance. The results are discussed with reference to potential explanatory mechanisms, study limitations, and future research needs.