This study explored the influence of adolescent mood variability on the symptom development of generalized anxiety and depression in the context of parent-adolescent negative interactions. Participants were 456 adolescents (55.7 % male) from a community sample, who were followed from age 13 to 16 years. During 4 annual assessments, adolescents reported on their generalized anxiety and depressive symptoms, and both parents and adolescents on levels of negative interactions with each other. Within each study year, adolescents rated their daily mood states during 5 consecutive days for 3 times per year (total of 9 weeks). The absolute differences between mood states on consecutive days were summed to construct a mood variability score. Results showed that high levels of adolescent mood variability predicted increases in generalized anxiety and depressive symptoms across the studied period. No influence of negative interactions on anxiety and depression development was found, but positive predictive links from mood variability to negative interactions at age 14 and 15 appeared. The study underscores the role of adolescent mood variability in the development of symptoms of generalized anxiety and depression during adolescence, but found little evidence for an influence of parent-adolescent negative interactions on internalizing problem development.