Self-regulation is central to many of the most important individual and societal problems today. We sought to determine whether the relationship between self-regulation and heart rate variability (HRV) could be replicated and extended. We hypothesized that baseline HRV would predict persistence on an anagram task, and that under conditions requiring greater self-control, HRV would increase. Two groups were given the same set of difficult and unsolvable anagrams. To induce self-regulatory fatigue, the suppression group was asked to try to not think of a white bear while the expression group was asked to try to think of a white bear. Baseline HRV predicted persistence on the unsolvable anagram. Both groups demonstrated changes in HRV relative to baseline, although we were unable to replicate findings that HRV was elevated during high self-regulatory effort. We were, however, able to replicate findings that the expression group persisted longer on the anagram task compared to the suppression group but only when accounting for physical activity scores. The present study advances our knowledge of the relationship between HRV and self-regulation, so that we can more successfully treat those with seriously impaired self-control.