Background:  This randomized controlled trial compared Hanen’s ‘More than Words’ (HMTW), a parent‐implemented intervention, to a ‘business as usual’ control group.

Methods:  Sixty‐two children (51 boys and 11 girls; M age = 20 months; SD = 2.6) who met criteria for autism spectrum disorders (ASD) and their parents participated in the study. The HMTW intervention was provided over 3.5 months. There were three measurement periods: prior to randomization (Time 1) and at 5 and 9 months post enrollment (Times 2 and 3). Children’s communication and parental responsivity were measured at each time point. Children’s object interest, a putative moderator, was measured at Time 1.

Results:  There were no main effects of the HMTW intervention on either parental responsivity or children’s communication. However, the effects on residualized gains in parental responsivity from Time 1 to both Times 2 and 3 yielded noteworthy effect sizes (Glass’s Δ = .71, .50 respectively). In contrast, there were treatment effects on child communication gains to Time 3 that were moderated by children’s Time 1 object interest. Children with lower levels of Time 1 object interest exhibited facilitated growth in communication; children with higher levels of object interest exhibited growth attenuation.

Conclusions:  The HMTW intervention showed differential effects on child communication depending on a baseline child factor. HMTW facilitated communication in children with lower levels of Time 1 object interest. Parents of children who evidence higher object interest may require greater support to implement the HMTW strategies, or may require different strategies than those provided by the HMTW curriculum.