Undernutrition is a confront to the health and output of the populace. It is viewed as one of the five leading contrary health impacts of climate variability and is defined as different measures of nutritional status. We aimed to assess the scientific evidence base for the impact of climate variability on childhood undernutrition (particularly wasting and underweight) in low- and middle-income countries. A systematic review was conducted to identify the peer-reviewed and gray full-text studies in English with no limits for the year of publication and study design. This review covers only published studies from four databases (PubMed, Scopus, Web of Science, and Science Direct). The risk of bias was assessed using the ROVBIS tool in individual studies. The PRISMA Statement checklist for systematic reviews was referred for this review process. A significant correlation between climate variables, temperature, rainfall, and drought, and at least one undernutrition parameter in 19 out of 22 studies was observed in this systematic review. In addition, we note that crop yield, maternal education, nutritional status of mothers, wealth status at the household level, and individual levels also play substantial roles in mediating the nutritional impacts. The findings of our analysis imply that exposure to climate variables may be linked to an increased risk of undernutrition both during and for several years following climate events. This may imply that undernutrition is never caused by temperature, precipitation, drought, or other weather-related factors alone but rather that undernutrition is triggered in children who are already at risk.