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.