Cognitive behavioural therapy (CBT) is an efficacious intervention for child anxiety that has been translated into accessible digital formats, many of which involve parents in treatment. However, the value of parental involvement in treatment is not clearly understood. This systematic review examined characteristics of parental involvement (i.e., format and content of sessions, level of therapist guidance, and parent session compliance) in digital CBT for child anxiety (mean child age ≤ 12 years) and their relation to child outcomes (primary disorder remission, clinician-, parent-, and child-rated anxiety, and global functioning). Systematic searches in CINAHL, Embase, ERIC, PsychINFO, PubMed, and Scopus up to 14th August 2023, and citation searching, identified 27 articles (as 23 studies) assessing 14 interventions. Two were parent-only programmes for 3–6-year-old children, with the remaining being parent–child programmes targeting older children. Parents were actively involved as coaches/collaborators, assisting their children with anxiety management and exposure, and less often as co-clients working on their own difficulties. Benefits of treatment were observed across interventions, except for one, psychoeducation-based programme. Higher remission rates were more frequently observed in interventions delivered in controlled settings, those with fewer parent-only sessions, or those incorporating more parent- or therapist-led exposure sessions. Most studies were conducted with affluent samples, limiting generalisability, and several received a high risk of bias rating. Future research should examine parent and family related mechanisms of change and modify interventions for improved adherence, such as restricting the number of modules parents are required to complete and teaching key therapeutic strategies such as exposure early in the programme.