The FEEL-KJ is an assessment instrument designed to measure emotion regulation (ER) strategies in children and adolescents. As the instrument was originally introduced as a self-report instrument, it is not yet known how self-reported ER strategies in the FEEL-KJ relate to parent-reported ER strategies. Yet, this is important for clinical practice, where combining multiple perspectives can give a better understanding of the situation. Here, we directly compared the self- and parent-report version of the FEEL-KJ by evaluating their reliability, the degree to which they correlate, and their complementarity in predicting emotional problems. We included both a community sample (N = 809) and a clinical sample (N = 60) of children (8–12 years) and adolescents (13–16 years), as well as their parents, who completed the self- and parent-report FEEL-KJ as measure of ER and the Child Behavior Checklist (CBCL; parent-report) and Child Depression Inventory (CDI; self-report) as measures of psychopathology. The results showed that both the self- and parent-report FEEL-KJ reliably measured ER. In addition, even though self- and parent-reported ER in the community sample primarily predicted emotional problems reported by the same informant, both ER reports could reliably distinguish between participants with and without clinical problems. Combining both types of ER report led to slightly better predictions of emotional problems. Taken together, these results show that ER in children and adolescents can be measured reliably via both self- and parent-report and that the two viewpoints provide complementary insights on emotional health.