Parenting support programmes are one of the most effective means of improving the mental health of caregivers and children. This study used a pre-post control group design with 970 participants to evaluate a group workshop programme (Support, not Perfection) designed to support caregivers of children zero to six in Serbia. Compared to those in the control group, parents who participated in the intervention reported significantly larger gains in positive parenting self-efficacy (e.g., empathy, positive discipline; Cohen d's range from 0.20 to 0.40), and decreases in depressive symptomatology and child behaviour problems (ds = -0.22). Programme effects did not differ based on caregiver gender, attendance (alone or with a co-parent), or challenges faced (levels of own depression or child's behavioural problems). These results suggest that "Support, not Perfection" is a scalable programme that can be used in low- and middle-income countries to improve parent and child well-being.