Technology-based interventions for Autism Spectrum Disorder (ASD) have proliferated, but few have been evaluated within the context of a randomised controlled trial (RCT). This RCT evaluated the efficacy of one technology-based early intervention programme (Therapy Outcomes By You; TOBY) in young children with ASD.TOBY is an app-based learning curriculum designed for children and parents as a complement to early behavioural intervention. Eighty children (16 female) were recruited to this RCT within 12 months of receiving a diagnosis of ASD (M age = 3.38; SD = 0.69) and randomised to receive either treatment-as-usual (community-based intervention, n = 39) or the TOBY therapy (at least 20 min/day) plus treatment-as-usual (n = 41) for a period of 6 months. Outcomes were assessed at 3 and 6 months postbaseline. (Australian New Zealand Clinical Trials Registry: ACTRN12614000738628; www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=365463).Children in the TOBY intervention group averaged 19 min/day engaging with the app in the first 3 months, but only 2 min/day during the second 3 months. There was no group difference in scores on the primary outcome, the Autism Treatment Evaluation Checklist, at either the 3- or 6-month follow-up. However, significant improvements at the 6-month follow-up were observed in the TOBY intervention group relative to the treatment-as-usual group on three secondary outcomes: the Fine Motor and Visual Reception subscales of the Mullen Scale of Early Learning and the Total Words Understood scale of the MacArthur-Bates Communicative Development Index. Statistical trends towards improvement in the TOBY intervention group were observed on measures of adaptive function, although these decreased in magnitude from the 3- to 6-month follow-up.This study provides evidence that technology-based interventions may provide a relatively low-cost addition to existing therapist-delivered interventions for children with ASD. However, sustained use of the app over the full 6-month period was a challenge for most families.