Resident-to-resident elder mistreatment (R-REM) in nursing homes is frequent and leads to adverse outcomes. Nursing home staff responses may significantly mitigate R-REM's impact, but little is known about current practices. The objective was to identify common staff responses to R-REM. The authors interviewed 282 certified nursing assistants (CNAs) in five urban nursing homes on their responses during the previous 2 weeks to R-REM behaviors of residents under their care. Ninety-seven CNAs (34.4%) reported actions responding to R-REM incidents involving 182 residents (10.8%), describing 22 different responses. Most common were physically intervening/separating residents (51), talking calmly to settle residents down (50), no intervention (39), and verbally intervening to defuse the situation (38). Less common were notifying a nurse (13) or documenting in behavior log (4). Nursing home staff report many varied responses to R-REM, a common and dangerous occurrence. CNAs seldom documented behaviors or reported them to nurses.