Introduction: While transitioning to adulthood presents challenges for youth with developmental disabilities (DD), opportunities to develop adult social roles and communication skills may foster more optimal outcomes. One such opportunity is developing conflict resolution skills within parent-adolescent relationships. Methods: We examined how reported conflict and observed conflict resolution behaviors differed between adolescents with typical development or DD, specifically intellectual disability (ID) and/or autism spectrum disorder, and their mothers. Participants (n = 167) were mid-adolescents (age 15) from a longitudinal study of how psychopathology develops in youth with or without DD. Results: While mothers' "Reported Conflict" was similar across groups, "Mother Problem Solving" was highest, and "Youth Problem Solving" lowest, in families of youth with ID. Higher "Reported Conflict" related to more negative observed conflict resolution behaviors across all groups. Conclusions: Results are considered in the context of transitioning to adulthood.