QUESTION: We compared the effectiveness of different types of parenting interventions based on an a priori taxonomy, and the impact of waitlists versus treatment as usual (TAU), in reducing child internalising problems. STUDY SELECTION AND ANALYSIS: We conducted a systematic review and network meta-analysis of published and unpublished randomised controlled trials (RCTs) until 1 October 2022 that investigated parenting interventions with children younger than 4 years. EXCLUSION CRITERIA: studies with children born preterm, with intellectual disabilities, or families receiving support for current abuse, neglect, and substance misuse. We assessed the certainty of evidence using the Confidence in Network Meta-Analysis framework. We used random-effects network meta-analysis to estimate standardised mean differences (SMDs) with 95% credible intervals (CrIs). FINDINGS: Of 20 520 citations identified, 59 RCTs (18 349 participants) were eligible for the network meta-analysis. Parenting interventions focusing on the dyadic relationship (SMD: -0.26, 95% CrI: -0.43 to -0.08) and those with mixed focus (-0.09, -0.17 to -0.02) were more effective in reducing internalising problems than TAU at the first time point available. All interventions were more effective than waitlist, which increased the risk of internalising problems compared with TAU (0.36, 0.19 to 0.52). All effects attenuated at later follow-ups. Most studies were rated as with 'high risk' or 'some concerns' using the Risk of Bias Assessment Tool V.2. There was no strong evidence of effect modification by theoretically informed components or modifiers. CONCLUSIONS: We found preliminary evidence that relationship-focused and mixed parenting interventions were effective in reducing child internalising problems, and the waitlist comparator increased internalising problems with implications for waiting times between referral and support. Considering the high risk of bias of most studies included, the findings from this meta-analysis should be interpreted with caution. PROSPERO registration number CRD42020172251