Objective: The aim of this pilot study was to evaluate a school-based intervention program focussing on reducing perfectionism in pre-adolescent children. Method: A 2-lesson intervention or the control condition was implemented across three schools (N = 125; M age = 11.60 years; 47.2% girls). Students completed assessments at baseline, post-intervention and 4-week follow-up. Results: Significant between group differences for self-oriented perfectionism-striving were identified post-intervention and were maintained at 4-week follow-up (d = 0.47 and 0.40 respectively). Significant interactions between group and time favouring the intervention group were identified for the hyperactivity and emotional problems. Discussion: Findings from this study provide preliminary support for the effectiveness of a perfectionism intervention at an earlier age than has been targeted to date. While these findings appear promising, the justification of such approaches with this age group will require follow-up investigations with expanded intervention content, longer follow-up assessments, larger samples, and evidence of impact on other variables such as well-being. Trial registration: ACTRN12614001262695.