Disordered eating (DE) and nonsuicidal self-injury (NSSI) commonly co-occur. This study compared several models of the longitudinal relationship between DE and NSSI, including concurrent and prospective models, and examined the possible moderating roles of self-objectification, impulsivity, and emotion dysregulation in these relationships. Individuals with NSSI (N = 197) recruited from online forums completed measures of NSSI and DE every 3 months for 1 year. We tested the associations between NSSI and DE using hierarchical linear models. Results supported a concurrent relationship, wherein frequency of NSSI positively covaried with concurrent DE severity. Body surveillance moderated the concurrent relationship between NSSI and DE. Individuals who engaged in more body surveillance endorsed high levels of DE pathology, whereas those lower in body surveillance engaged in more frequent NSSI only at higher levels of DE. In addition, whereas DE did not prospectively predict NSSI, frequency of NSSI predicted more severe DE 3 months later. The prospective relationship between DE and later NSSI was moderated by emotion dysregulation, such that highly dysregulated individuals had a stronger relationship between DE and later NSSI, whereas this relationship was not significant among individuals low in emotion dysregulation. These findings add valuable information regarding the co-occurrence of self-damaging behaviors.