Objective: To compare Phase 1 treatment, using the Frankel 2 (FR2) or the modified Twin Block (MTB), for Class II division 1 malocclusion in children and adolescents with respect to: treatment duration, number of appliance breakages, occlusal outcome, and patient and parent perspectives.Materials and Methods: Sixty participants with a Class II division 1 malocclusion were randomly assigned to either the FR2 or MTB appliance in a two-armed parallel randomized clinical trial with an allocation ratio of 1 to 1. Time to achieve a Class I incisor relationship was the primary outcome. The number of appliance breakages was recorded. The Peer Assessment Rating (PAR) index was used to evaluate pre- and post-treatment occlusal outcome on study models. Participants completed the child OHRQoL (oral health-related quality of life), Piers-Harris, Standard Continuum of Aesthetic Need (SCAN), and Oral Aesthetic Subjective Impact Score (OASIS) questionnaires pre- and post-treatment; parents completed a SCAN questionnaire.Results: Forty-two participants completed treatment (FR2: 20; MTB: 22). Multiple imputation was used to impute missing data for noncompleters. Mean treatment duration was similar for the two appliances (FR2: 376 days [SD 101]; MTB: 340 days [SD 102]; P = .41). There were no significant differences in mean number of appliance breakages (FR2: 0.3 SD 0.7; MTB: 0.4 SD 0.8; P = .67 or mean PAR score P = .48). Patient and parent perspectives did not differ between appliances (P >.05).Conclusions: Phase 1 treatment duration, number of appliance breakages, occlusal outcome, and patient and parent perspectives were similar in 11-14 year olds with Class II division 1 malocclusion treated using the FR2 or MTB appliance.