Background Systemic lupus erythematosus (SLE) and juvenile idiopathic arthritis (JIA) are the most common rheumatological diseases in children, requiring prolonged treatment. Quality of life (QoL) is an important factor in treating rheumatological diseases. Currently, only few QoL data on the effects of such disease in adolescents. Objective To assess QoL in adolescents with rheumatological diseases, as well its associations with disease severity and disease duration. Methods A cross-sectional study was conducted in patients diagnosed with SLE or JIA during August-November 2021 at the Allergy and Immunology Polyclinic, Department of Child Health, Cipto Mangunkusumo Hospital. Inclusion criteria were all patients age 10-18 with SLE or JIA. Quality of life was assessed using PedsQL-RM questionnaire filled by patients and their parents online by mobile phone. Results Of 82 adolescent subjects who filled questionnaires, 91.4% had SLE and 8.6% had JIA disease. Approximately 65.9% of all subjects with rheumatological diseases and 69.3% of the SLE patients had a good QoL, while 70.7% had low-moderate disease activity. Only 2/7 JIA patients had a good quality of life, while 4/7 JIA patients had high disease activity. The PedsQL-RM aspects of care and communication had lower scores than those of the other aspects, but they were still not significantly correlated to disease activity (P=0.883). Disease duration was also not associated with overall QoL (P=0.392) Conclusion Most of adolescents with rheumatological disease (SLE and JIA) had a good QoL. Disease activity and duration were not associated with QoL as measured by the PedsQL-RM questionnaire.