Abstract Objective This study sought to assess maternal growth monitoring knowledge and its effect on stunting, wasting and underweight among children 0–18 months in the Tamale Metropolis. An analytical cross-sectional study design, involving 340 mother–child pairs randomly selected from 4 health facilities in the Tamale Metropolis was used. A structured questionnaire was used to collect information on socio-demographic characteristics and maternal growth monitoring knowledge. Weight and length of children were taken to assess nutritional status (stunting, underweight and wasting). Chi square/Fisher’s exact test was used to determine the association between maternal growth monitoring knowledge level and child nutritional status. Results The study revealed that 87.6% of mothers had good knowledge on growth monitoring. The prevalence of stunting, underweight and wasting were 9.4%, 25.9% and 17.9% respectively. Bivariate analysis revealed that there is no association between maternal growth monitoring knowledge and stunting (p = 0.781), wasting (p = 0.743) and underweight (p = 0.529) among children 0–18 months in the Tamale Metropolis.