Infancy is a critical stage of life, and a secure relationship with caring and responsive caregivers is crucial for healthy infant development. Early parenting interventions aim to support families in which infants are at risk of developmental harm. Our objective is to systematically review the effects of parenting interventions on child development and on parent-child relationship for at-risk families with infants aged 0-12 months. Design This is a systematic review and meta-analyses. We extracted publications from 10 databases in June 2013, January 2015 and June 2016, and supplemented with grey literature and hand search. We assessed risk of bias, calculated effect sizes and conducted meta-analyses. Inclusion criteria (1) Randomised controlled trials of structured psychosocial interventions offered to at-risk families with infants aged 0-12 months in Western Organisation for Economic Co-operation and Development (OECD) countries, (2) interventions with a minimum of three sessions and at least half of these delivered postnatally and (3) outcomes reported for child development or parent-child relationship. Results Sixteen studies were included. Meta-analyses were conducted on seven outcomes represented in 13 studies. Parenting interventions significantly improved child behaviour (d=0.14; 95% CI 0.03 to 0.26), parent-child relationship (d=0.44; 95% CI 0.09 to 0.80) and maternal sensitivity (d=0.46; 95% CI 0.26 to 0.65) postintervention. There were no significant effects on cognitive development (d=0.13; 95% CI 0.08 to 0.41), internalising behaviour (d=0.16; 95% CI 0.03 to 0.33) or externalising behaviour (d=0.16; 95% CI 0.01 to 0.30) post-intervention. At long-term follow-up we found no significant effect on child behaviour (d=0.15; 95% CI 0.03 to 0.31). Conclusions Interventions offered to at-risk families in the first year of the child's life appear to improve child behaviour, parent-child relationship and maternal sensitivity post-intervention, but not child cognitive development and internalising or externalising behaviour. Future studies should incorporate follow-up assessments to examine long-term effects of early interventions.