Although psychoeducational interventions are recommended as Phase 1 interventions for complex trauma, there is limited evidence on their efficacy. This pilot randomized control trial (RCT) investigated the efficacy of a pure psychoeducational intervention for complex trauma. A brief 10‐session intervention was delivered to n = 44 female prisoners in a compressed format to accommodate short sentence lengths and was compared with usual care (n = 42). Results from an intent‐to‐treat (ITT) analysis indicated that there were no statistically significant differences between the two arms across the three assessment time points (including 1‐month postintervention) for the main outcomes (Behavioural Assessment Checklist‐Revised, β = 4.60, 95% CI [−1.60, 10.88], p = .148; posttraumatic stress disorder [PTSD] Checklist, β = −1.47, 95% CI [−4.30, 1.36], p = .303). Post hoc reliable change analyses suggested twice the number of adequate dose participants made progress in addressing PTSD symptoms compared with usual care (30.3% vs. 17.6%, OR 2.03, 95% CI [.64, 6.43]). Although further work in this area is required, initial results, overall, suggest that psychoeducational group‐based treatment modalities achieve only small effect sizes in comparison with usual care.