IMPORTANCE Reducing child exposure to tobacco smoke is a public health priority. Guidelines recommend that health care professionals in child health settings should address tobacco smoke exposure (TSE) in children. OBJECTIVE To determine the effectiveness of interventions delivered by health care professionals who provide routine child health care in reducing TSE in children. DATA SOURCES A secondary analysis of 57 trials included in a 2014 Cochrane review and a subsequent extended search was performed. Controlled trials (published through June 2015) of interventions that focused on reducing child TSE, with no restrictions placed on who delivered the interventions, were identified. Secondary data extraction was performed in August 2015. STUDY SELECTION Controlled trials of routine child health care delivered by health care professionals (physicians, nurses, medical assistants, health educators, and dieticians) that addressed the outcomes of interest (TSE reduction in children and parental smoking behaviors) were eligible for inclusion in this review and meta-analysis. DATA EXTRACTION AND SYNTHESIS Study details and quality characteristics were independently extracted by 2 authors. If outcome measures were sufficiently similar, meta-analysis was performed using the random-effects model by DerSimonian and Laird. Otherwise, the results were described narratively. MAIN OUTCOMES AND MEASURES The primary outcome measure was reduction in child TSE. Secondary outcomes of interest were parental smoking cessation, parental smoking reduction, and maternal postpartum smoking relapse prevention. RESULTS Sixteen studies met the selection criteria. Narrative analysis of the 6 trials that measured child TSE indicated no intervention effects relative to comparison groups. Similarly, meta-analysis of 9 trials that measured parental smoking cessation demonstrated no overall intervention effect (n = 6399) (risk ratio 1.05; 95% CI, 0.74-1.50; P = .78). Meta-analysis of the 3 trials that measured maternal postpartum smoking relapse prevention demonstrated a significant overall intervention effect (n = 1293) (risk ratio 1.53; 95% CI, 1.10-2.14; P = .01). High levels of study heterogeneity likely resulted from variability in outcome measures, length of follow up, intervention strategies, and unknown intervention fidelity. CONCLUSIONS AND RELEVANCE Interventions delivered by health care professionals who provide routine child health care may be effective in preventing maternal smoking relapse. Further research is required to improve the effectiveness of such interventions in reducing child TSE and increasing parental smoking cessation. The findings of this meta-analysis have policy and practice implications relating to interventions by routine pediatric health care professionals that aim to reduce child exposure to tobacco smoke.