The experience of pain during nonsuicidal self-injury (NSSI) remains enigmatic. Ultimately, there is a dearth of evidence regarding whether pain is actually experienced during NSSI behavior and, if it is, to what extent that pain offsets following cessation of the NSSI episode. Using a smartphone app to collect information on self-injury episodes reported by adolescents and young adults in their daily lives, we found that across 143 NSSI episodes comprising 442 NSSI behaviors, most participants reported feeling significant and substantial pain onset during most NSSI episodes. A small effect was established for pain offset, with pain diminishing somewhat for most at NSSI completion. Furthermore, those who had higher negative emotion at the start of NSSI episodes but experienced less pain onset reported more NSSI behaviors during such episodes. The evidence supports a dynamic experience of pain during self-injury that can vary between people and episodes.