Kidnapping is a common tactic used by insurgent groups. However, why insurgents commit kidnappings remains insufficiently understood. Based on 1,386 group-year observations of 140 insurgents between 1998 and 2012, we analyze conditions driving the within-group temporal changes in their involvement (1 vs 0) versus event-frequency in kidnappings. We find that changes in specific quasi-state activities (i.e., extraction and provision of public services), which may rely on kidnappings for coercive enforcement and social control, predict kidnapping “involvement” only. Meanwhile, general resource and capacity conditions (i.e., territory-control, criminal networks and combat-lethality) influence changes in both kidnapping involvement and event-frequency.