Background: Grandparents have a significant role in providing regular child care to their grandchildren. As such, they are in a unique position to help with the prevention of child disruptive disorders. However, the child-care role grandparents provide can also negatively impact the grandparent-parent relationship. Aims: This case study examined the impact of a parenting program designed specifically for grandparents on a grandparent providing regular child care to her granddaughter. Method: A case study is presented of a 56-year-old grandmother providing between 31-40 hours of care per week to her granddaughter, who is at risk of developing an early onset child disruptive disorder. The grandparent was measured on outcomes of child behaviour; parenting style; parenting confidence; psychological wellbeing in terms of stress, depression, and anxiety; and relationship satisfaction with the parent. The parent was also measured on child behaviour outcomes and relationship satisfaction with the grandparent. Measures were given at baseline, post-intervention, and at 6-month follow-up. Results: The grandparent reported significant reductions in stress, anxiety and depression; improved relationship satisfaction with the parent; and decreased reliance on dysfunctional parenting practices. The parent also reported decreased child behaviour problems and increased relationship satisfaction with the grandparent. No findings were found for parenting confidence. Conclusion: This case study provides encouraging findings for a new parenting program designed specifically for grandparents, and it is recommended that future research evaluate its efficacy in a randomised controlled trial.