This study examined caregiver strain in families who initiated mental health services for their child. Predictors of strain and the bidirectional relation between strain and child symptoms were examined. Participants included 218 children aged 4 to 13 with disruptive behavior problems and their caregivers, plus 96 psychotherapists, recruited from six publicly funded clinics. Child disruptive behavior severity and caregiver strain were assessed at baseline, 4, and 8 months. Multilevel models were used to examine predictors of reduced caregiver strain, and autoregressive cross-lagged models were used to examine the bidirectional relations between change in caregiver strain and behavior problems over time. There were small to medium decreases in caregiver strain over the 8 months after the initiation of mental health services, but few factors predicted change other than initial behavior problem severity. Whereas more severe initial child symptoms predicted greater reductions in caregiver strain, greater child symptom severity sustained at 4 months predicted lesser improvements in caregiver strain. Simultaneously, greater caregiver strain predicted less improvement in child symptom severity, suggesting that child symptom severity and caregiver strain affect each other over time. These results suggest that attending to both child and caregiver factors may be important in maintaining improvements after initiating usual care.