Abstract Objective Due to systemic inequities, Black adolescents with type 1 diabetes are more likely to have suboptimal glycemic control and high rates of diabetes distress, but tailored interventions for this population are lacking. In primary outcomes of a randomized clinical trial, a family-based eHealth intervention improved glycemic control in Black adolescents with type 1 diabetes and elevated depressive symptoms. The present study is a secondary analysis of these clinical trial data examining the moderating effect of diabetes distress on the efficacy of the intervention. Methods Using secondary data from a multicenter randomized clinical trial (Clinicaltrials.gov [NCT03168867]), caregiver–adolescent dyads were randomly assigned to either up to three sessions of an eHealth parenting intervention (n = 75) or a standard medical care control group (n = 74). Black adolescents (10 years, 0 months to 14 years, 11 months old) with type 1 diabetes and a caregiver willing to participate were eligible. Adolescents reported their diabetes distress at baseline, and hemoglobin A1c (HbA1c) data were collected at baseline, 6-, 13-, and 18-month follow-up. Results No between-group contrasts emerged in a linear mixed-effects regression (p’s > .09). Within-group contrasts emerged such that adolescents assigned to the intervention who reported high diabetes distress had lower HbA1c at the 18-month follow-up relative to baseline (p = .004); the 18-month decrease in HbA1c was −1.03%. Conclusions Black adolescents with type 1 diabetes and high levels of diabetes distress showed significant decreases in HbA1c following a family-based eHealth intervention, suggesting diabetes distress may be a key moderator of intervention efficacy within this population.