Recent investigations have shown little evidence that written disclosure benefits bereaved individuals over a control condition. The present study hypothesized that the effectiveness of written disclosure for bereavement may be moderated by vagal tone, as indexed by respiratory sinus arrhythmia (RSA). Vagal tone has been identified as an important individual difference in depression. The present study investigated 35 bereaved participants in a longitudinal design, with participants writing each week for 3 weeks, and then participating in follow-up sessions 1 week and 1 month later. As with previous studies, bereaved participants showed improvement, although no differential improvement was seen in the emotional Disclosure group compared to a Control writing group. As hypothesized, however, those participants with the highest RSA benefited most from the written disclosure, while RSA level did not predict outcome in the control condition. Future research should investigate whether vagal tone moderates the impact of written disclosure for non-bereaved individuals.