The critical role of executive functioning in autism as well as the co-occurring mental health challenges common among autistic youth support to the immense value of interventions targeting executive functioning for enhancing mental health services for autistic children. The goal of the present study was to conduct a randomized feasibility trial of "Unstuck and On Target," an executive functioning intervention, adapted for delivery in children's community mental health setting. Mental health therapists (n = 26) enrolled with participating autistic clients (n = 32) were randomized to receive training in and deliver the adapted "Unstuck" intervention or to deliver care as usual. We completed masked observational measures of "Unstuck" strategy use (fidelity) during recorded sessions of participating therapist-client dyads and collected measures of acceptability from participating clients and their caregivers. We also collected measures of pre-post changes in executive functioning and mental health symptoms. Therapists trained in "Unstuck" demonstrated significantly higher use of "Unstuck" strategies compared to usual care therapists. Caregivers and autistic clients perceive adapted "Unstuck" as highly acceptability and helpful. Autistic clients whose therapists were trained in adapted "Unstuck" demonstrated larger pre-post changes in executive functioning compared to usual care. Across all participating clients, changes in executive functioning were significantly related to changes in mental health symptoms. Finally, clients of therapists trained in adapted "Unstuck" demonstrated moderate improvements in overall mental health symptoms. The current study provides preliminary evidence of the feasibility and impact of "Unstuck and On Target" for children's community mental health settings.