Successful recognition is generally thought to be based on both recollection and familiarity of studied information. Recent studies found that making judgments of learning (JOLs) can reactively facilitate recognition performance, a form of reactivity effect on memory. The current study aimed to explore the roles of recollection and familiarity in the "reactivity effect" on recognition performance. Experiment 1 replicated the positive reactivity effect on recognition performance. Experiment 2 used the sequential remember/know (R/K) procedure, Experiment 3 utilized the simultaneous R/K procedure, and Experiment 4 inserted a long study-test interval (i.e., 24-h) to determine the roles of recollection and familiarity in the reactivity effect. These three experiments converged in demonstrating that making JOLs reactively facilitated recognition performance through enhancing both recollection and familiarity. Furthermore, there was minimal difference between the reactive influences on recollection and familiarity. The documented findings imply that the JOL reactivity effect on recognition is supported by two underlying mechanisms: greater recollection induced by enhanced distinctiveness, and superior familiarity induced by enhanced learning engagement.