Self-control is the ability to inhibit self-defeating behavior in the face of temptation. The neural basis of self-control remains elusive, due to the difficulty of disentangling the processes of self-control and choice based on cost-benefit evaluations. We designed a novel task in monkeys that can distinguish different self-control levels from subjective preference. We found that Supplementary Eye Field neurons encode self-control, some even before choice options were presented. This neuronal activity predicted whether and when monkeys would give in to temptation. Our findings suggest that Supplementary Eye Field is part of a neuronal circuit underlying the capacity for self-control, which is crucial for selecting and maintaining the pursuit of costly goals that are beneficial in the long run.