The use of growth monitoring and promotion (GMP) services in the first two years of life can facilitate the early identification of common childhood health issues such as malnutrition and infections. It also creates an opportunity to promote education and nutritional counselling. This study is the first to investigate the use of GMP and its influencing factors among mothers in Ethiopia’s pastoralist regions, including the Afar National and Regional State, where childhood malnutrition is a significant cause of morbidity and mortality. Between May and June 2021, a cross-sectional study was conducted within the Semera-Logia city administration. The study used a random sampling technique to select 396 children under two, and data were gathered using an interviewer-administered questionnaire. Multivariable logistic regression was used to analyse the influence of explanatory variables, which included socio-demographic, health service, and health literacy factors, on the utilisation of GMP services. The overall utilisation of GMP services was 15.9% (95% confidence intervals [CI]: 12.0%, 19.5%). Children whose fathers had college or higher education were more likely to utilise GMP services (adjusted odd ratios [AOR] = 7.75; 95% CI: 3.01, 19.99), whereas children living in households with more children were less likely to utilise GMP services (AOR = 0.11; 95% CI: 0.04, 0.28 for households with 3–4 children and AOR = 0.23; 95% CI: 0.08, 0.67 for households with 4+ children). Children who received postnatal care had higher odds of GMP service use (AOR = 8.09; 95% CI: 3.19, 20.50). GMP services are not being fully utilised to decrease infant and child morbidity and mortality caused by malnutrition in Ethiopia. We recommend strengthening GMP services in Ethiopia and taking targeted action to address the low attainment of parental education and poor postnatal care utilisation. Public health initiatives such as the implementation of mobile health (mHealth) approaches and education of mothers by female community healthcare workers on the significance of GMP services could be effective in increasing GMP service utilisation.