Background: Drugs with histone deacetylase inhibitory (HDACi) properties have shown to decrease prostate cancer (PCa) cell growth in vitro. Methods: A cohort of 9261 PCa cases from the Finnish Randomized Study of Screening for Prostate Cancer (FinRSPC) was used to evaluate prostate cancer-specific mortality in men using anti-epileptic drugs (AEDs). A national subscription database was used to obtain information on medication use. Cox regression with AED use as a time-dependent variable was used to analyse prostate cancer mortality in men using AEDs compared to non-users, and in men using HDACi AEDs compared to users of other AEDs. The analysis was adjusted for age, screening trial arm, PCa risk group, primary treatment of PCa, Charlson co-morbidity score and concomitant use of other drugs. Results: The use of AEDs, in general, was associated with an increased risk of PCa death. The use of HDACi AEDs was not significantly associated with decreased PCa mortality compared to use of other AEDs (HR 0.61, 95% CI 0.31–1.23). Conclusions: AED usage is associated with elevated PCa mortality compared to non-users, likely reflecting the differences between men with epilepsy and those without. No benefit was observed from HDACi drugs compared to other AEDs.