Background: In tackling the ongoing malnutrition problem in many parts of Kenya, the government has initialized preventive actions such as mother support groups in order to improve health and nutrition among children. Few studies have evaluated the effectiveness of such intervention. Objective: This study aimed at determining how mother support groups affect the nutrition status of children under 2 years of age. Methods: 41 children participated. Anthropometric measurements were taken of the children once a month during 12 months. Medical history, nutrition status and socioeconomic factors were collected by interviews with the mothers. The children were divided into two groups depending on their mother's assigned group; mother support group or not. Results: Nutritional status was significantly better among children in the mother support group (P=0.001). There were significantly more children with severe acute malnutrition among the children not in support group (P=0.040). The mean height (P=0.001) and mean weight (P=0.0281) were significantly higher among children in the non-support group. Conclusion: Mother support groups may have a beneficial effect on the nutritional status of children under 2 years of age. Cases of severe acute malnutrition seemed to be less prevalent in children whose mothers attend mother support groups.