Experimental studies suggest alcohol facilitates deliberate self-harm (DSH). One explanation might be that alcohol increases pain tolerance (PT), which may then lead to DSH. This study aimed to examine whether PT mediated the relationship between alcohol and DSH. Further, alcohol is neither necessary nor sufficient to self-harm. Given past non-suicidal self-injury (NSSI) is a good predictor of future DSH, NSSI may moderate these relationships. This study also aimed to examine if mediation was conditional upon past NSSI. Participants (106 men and 104 women) reported on past NSSI and received a drink sufficient to produce target blood-alcohol content (BAC = .000%, .050%, .075%, or .100%). Participants completed a behavioral measure of DSH. Results revealed that the association between BAC and DSH was mediated through PT. Additionally, past NSSI moderated the path between PT and DSH but did not affect the path between BAC and PT. Clinical implications and limitations are discussed.