This pilot RCT compared the effect of a self-directed and therapist-assisted telehealth-based parent-mediated intervention for young children with ASD. Families were randomly assigned to a self-directed or therapist-assisted program. Parents in both groups improved their intervention fidelity, self-efficacy, stress, and positive perceptions of their child; however, the therapist-assisted group had greater gains in parent fidelity and positive perceptions of child. Children in both groups improved on language measures, with a trend towards greater gains during a parent–child interaction for the therapist-assisted group. Only the children in the therapist-assisted group improved in social skills. Both models show promise for delivering parent-mediated intervention; however, therapist assistance provided an added benefit for some outcomes. A full-scale comparative efficacy trial is warranted.