This study examined the effects of strategic, motivational self-talk for runners completing a 60-mile, overnight ultramarathon using a randomized, controlled experiment. Data were collected before, during, and after an annual ultramarathon. Twenty-nine ultramarathon runners were randomly allocated to a motivational self-talk group or an alternative control group. A condition-by-time mixed ANOVA indicated that learning to use motivational self-talk did not affect preevent self-efficacy or perceived control. A t-test and magnitude-based inference indicated that motivational self-talk did not affect performance. Nevertheless, follow-up data suggested that most participants found the intervention helpful and continued to use it six months after their research commitment, particularly in endurance events and to a lesser extent in training. Participants continued to use self-talk to cope with exertion, as well as other stressors such as blister discomfort and adverse conditions. Suggestions are offered for future research examining the effects of psychological interventions on performance in endurance events.