Recent research on the patterns of self-harm around public holidays is lacking. This study used national data to examine the patterns of hospital-treated self-harm during public holidays, and to examine associated factors. Data on self-harm presentations to all emergency departments were obtained from the National Self-Harm Registry Ireland. The association between self-harm presentations and public holidays was examined using univariate and multivariate Poisson regression analyses. A total of 104,371 presentations of self-harm were recorded between 2007 and 2015. The mean number of self-harm presentations was 32 on public holidays. St. Patrick's Day had the highest number of presentations compared to all other public holidays, with a daily mean of 44 presentations. Across all years, self-harm presentations during public holidays had a 24% increased risk of involving alcohol consumption compared to all other days and this effect was most pronounced during the Christmas period. The association with alcohol remained significant at a multivariate level. Presentations on public holidays were more likely to attend out of normal working hours. An increase in male presentations involving self-cutting was observed on public holidays and there was an over-representation of males presenting for the first time. It is likely that extent of alcohol involvement in self-harm presentations reported here is an underestimate, as it was dependent on the information being recorded by the attending clinician. Public holidays are associated with an elevated number of self-harm presentations to hospital, with presentations to hospital involving alcohol significantly increased on these days. Hospital resources should be targeted to address increases during public holidays, including during out-of-hours. Involvement of alcohol may delay delivery of care to these patients in emergency settings.