Children engage cognitive control reactively when they encounter conflicts; however, they can also resolve conflicts proactively. Recent studies have begun to clarify the mechanisms that support the use of proactive control in children; nonetheless, sufficient knowledge has not been accumulated regarding these mechanisms. Using behavioral and pupillometric measures, we tested the novel possibility that 5-year-old children (N = 58) learn to use proactive control via the acquisition of abstract task knowledge that captures regularities of the task. Participants were assigned to either a proactive training group or a control training group. In the proactive training group, participants engaged in a training phase where using proactive control was encouraged, followed by a test phase using different stimuli where both proactive and reactive control could be used. In the control training group, participants engaged in a training phase where both cognitive control strategies could be used, followed by a similarly-structured test phase using different stimuli. We demonstrated children in the control training group responded more quickly and accurately and showed greater cue-related pupil dilation in the test phase than in the training phase. However, there were no differences in response times, accuracies, and pupil dilation between the proactive and control training groups in the training and test phases. These findings suggest that prior task experience, that goes beyond specific knowledge about the timing of task goal activation, can lead children to engage more proactive control endogenously, even if they are not directly encouraged to do so.