Background Type 1 diabetes is associated with significant mortality and economic cost. Management of type 1 diabetes involves completing multiple daily adherence behaviors, and many adolescents struggle with self-management and show poor glycemic control. Purpose The purpose was to conduct an unblinded pilot randomized controlled parallel-group study of a web-delivered multicomponent intervention targeting self-monitoring of blood glucose, working memory, and parent supervision of diabetes care among adolescents with type 1 diabetes. Intervention components included high magnitude incentives for adolescents and parents, motivational and cognitive behavioral therapy and working memory training for adolescents, and training in contingency contracting for parents. Methods Adolescents (N = 114) with poorly controlled type 1 diabetes were screened, and N = 61 were randomized using minimum likelihood allocation to usual care (usual care, N = 31) or to a 25-week/15-session web-delivered intervention (WebRx, N = 30). Results At the end of treatment, adolescents in WebRx had higher self-monitoring of blood glucose (d = 0.58) (primary outcome), better visual spatial working memory (d = 0.48) and inhibition (d = 0.98), and lower HbA1c (d = 0.45) than those in usual care. WebRx parents reported more frequent review of the adolescent's glucometer (d = 1.30) and reduced family conflict (d = 0.56). Between-condition differences were maintained 6 months later in self-monitoring of blood glucose (d = 0.42), visual spatial working memory (d = 0.76), family conflict (d = 0.50), and HbA1c (d = 0.44). Conclusions Results showing sustained effects on self-monitoring of blood glucose and HbA1c support moving forward with a larger trial to test this innovative web-delivered and multicomponent intervention.