Few studies have investigated body-dysmorphic, hoarding, hair-pulling, and skin-picking symptoms in adolescents and how they relate to mental health, quality of life, suicide attempts, and non-suicidal self-harm. We used a quota sampling procedure and contacted 100 secondary centres in the Southeast of Spain, of which 34 participated in the study. A sample of 5,345 adolescents (12–18 years) completed dimensional measures of body-dysmorphic, hoarding, hair-pulling, and skin-picking symptoms. The proportion of adolescents with clinically significant symptoms within each symptom type was estimated and associations with other indicators of mental health examined. Clinically significant body-dysmorphic symptoms were reported by 3.7%, hoarding by 0.9%, hair-pulling by 0.7%, and skin-picking by 1.8%. Body-dysmorphic symptoms were more common in girls and in those over 14 years of age. Body-dysmorphic, hoarding, hair-pulling, and skin-picking symptoms were moderately to strongly associated with obsessive-compulsive symptoms, internalizing symptoms, externalizing symptoms, and poor quality of life. Those with significant body-dysmorphic, hoarding, hair-pulling, and skin-picking symptoms were much more likely to have attempted suicide and engaged in non-suicidal self-harm during the last twelve months than those without such symptoms. Body-dysmorphic symptoms showed the strongest associations with internalizing symptoms and poor quality of life. Limitations are the sole use of self-report and a sample from only two regions in Spain, but findings suggest that body-dysmorphic, hoarding, hair-pulling, and skin-picking symptoms are common and impairing during adolescence.