<p>Core features of callous-unemotional (CU) traits (e.g., low empathy, lack of guilt, callousness) are underpinned by emotion processing deficits including dysfunction in emotion reactivity (ERc) and emotion regulation (ER). Recent research has suggested the presence of heterogeneity in CU traits, such that the primary variant is biologically rooted and marked by hypoarousal, whereas the secondary variant develops as a response to maltreatment and is marked by hyperarousal. To date, physiological measurement of ERc and ER processes via the parasympathetic nervous system have focused on static methods of measurement; however, dynamic approaches may provide a more nuanced picture of reactive and regulatory processes. The current study sought to identify whether youth with primary versus secondary CU trait variants differed on ERc and ER as indexed by both static and dynamic objective physiological markers with the goal of improving our understanding of CU trait development and informing future treatment targets. Participants consisted of 636 youth ages 12–18 recruited from a juvenile detention center. A latent profile analysis identified primary and secondary CU groups using CU traits, anxiety, and posttraumatic arousal and avoidance. Groups were subsequently compared on static and dynamic respiratory sinus arrhythmia (RSA) indices of ERc and ER. Only one dynamic measure of ER (i.e., RSA inertia) uniquely differentiated youth with primary and secondary traits, whereas static measures provided little discriminative utility. The current findings provide a more comprehensive understanding of CU trait heterogeneity with respect to emotion processing, allowing us to more effectively target CU traits in the treatment context.</p>