Affect dysregulation in response to rewarding stimuli has been proposed as a vulnerability factor for major depressive disorder (MDD). However, it remains unclear how affective behavioral dynamics may be altered among individuals who are at high risk for depression but not currently depressed. We examined the dynamics of affective facial behavior during hedonic probes among 3 groups of adolescents: remitted probands who had histories of childhood-onset MDD (n = 187), never-depressed siblings of probands (high familial risk; n = 207), and healthy controls (n = 166). Participants' happy and sad facial expressions were coded during 3 hedonic laboratory tasks: receiving a preferred prize, describing a positive autobiographical memory, and watching a humorous film. Happy and sad behavioral dynamics were indexed by mean level- and time-dependent reactivity, variability (mean of the squared successive differences), and inertia (autocorrelation). Relative to controls, probands and siblings exhibited a more rapid decrease in happy behaviors, and probands exhibited higher inertia of sad behaviors during hedonic probes. Both probands and siblings exhibited lower inertia of sad behaviors while receiving a desired prize, which highlights the importance of context variation in testing hypotheses. Overall, our study provides new evidence that hedonic behavioral dysregulation, as reflected in dynamic facial behavior, may highlight depression vulnerability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).