Background: The need to improve the quality of foster care training has been highlighted and evidenced-based programs that aim to support foster carers in the care of children who have experienced trauma are warranted. Objective: This study aimed to evaluate the effectiveness of the Fostering Connections program, a newly developed trauma-informed care program within the national child welfare agency in Ireland. Participants and setting: The study included 79 foster carers. The Fostering Connections group-based experiential intervention was delivered over a period of 6-weeks in a community-based setting to intervention group participants. Methods: A quasi-experimental design was used to compare the results of the intervention group (n = 49), to a control group (n = 30,) who received usual care. Standardized assessment measures were used at baseline, 6-weeks on completion, 16 weeks and 15 months post-intervention. Foster carers’ knowledge of trauma-informed fostering, tolerance of misbehavior and fostering efficacy, and children's emotional and behavioral difficulties were assessed. Results: Significant improvements were found in foster carers’ knowledge of trauma-informed fostering (p < 0.001), tolerance of child misbehavior (p = 0.007) and fostering efficacy (p < 0.001), with effect sizes ranging from medium to large and sustained over fifteen months (ES = 0.07–0.14). Significant improvement was also found in children's emotional and behavioral difficulties at fifteen months (p = 0.019), with a small effect size (ES = 0.05). Conclusion: Preliminary evidence suggests that Fostering Connections is potentially an effective intervention in increasing foster carer's capacity to provide children with trauma-informed care.