Objective: To evaluate (1) the longitudinal relationship between parental well-being and glycemic control in youth with type 1 diabetes and (2) if youth's problem behavior, diabetes parenting behavior, and parental diabetes-distress influence this relationship. Research Design and Methods: Parents of youth 8-15 yrs (at baseline) (N = 174) participating in the DINO study completed questionnaires at three time waves (1 yr interval). Using generalized estimating equations, the relationship between parental well-being (WHO-5) and youth's HbA1c was examined. Second, relationships between WHO-5, Strength and Difficulties Questionnaire (SDQ), Diabetes Family Behavior Checklist (DFBC), Problem Areas In Diabetes-Parent Revised (PAID-Pr) scores, and HbA1c were analyzed. Results: Low well-being was reported by 32% of parents. No relationship was found between parents' WHO-5 scores and youth's HbA1c (β = -0.052, p = 0.650). WHO-5 related to SDQ (β = -0.219, p < 0.01), DFBC unsupportive scale (β = -0.174, p < 0.01), and PAID-Pr (β = -0.666, p < 0.01). Both DFBC scales (supportive β = -0.259, p = 0.01; unsupportive β = 0.383, p = 0.017), PAID-Pr (β = 0.276, p < 0.01), and SDQ (β = 0.424, p < 0.01) related to HbA1c. Conclusions: Over time, reduced parental well-being relates to increased problem behavior in youth, unsupportive parenting, and parental distress, which negatively associate with HbA1c. More unsupportive diabetes parenting and distress relate to youth's problem behavior.