The objective of the study was to investigate the association between maternal common mental disorder (CMD) and infant growth in rural Malawi. A cross-sectional study was conducted at a district hospital child health clinic. Participants were consecutive infants due for measles vaccination, and their mothers. Mean infant weight-for-age and length-for-age z-scores were compared between infants of mothers with and without CMD as measured using the self-reporting questionnaire (SRQ). Of 519 eligible infants/mothers, 501 were included in the analysis. Median infant age was 9.9 months. 29.9% of mothers scored 8 or above on the SRQ indicating CMD. Mean length-for-age z-score for infants of mothers with CMD (-1.50 SD 1.24) was significantly lower than for infants of mothers without CMD (-1.11 SD 1.12) Student's t-test: P = 0.001. This association was confirmed in multivariate analysis. Mean weight-for-age z-score for infants of mothers with CMD (-1.77 SD 1.16) was lower than for infants of mothers without CMD (-1.59 SD 1.09) but this difference was not significant on univariate (Student's t-test: P = 0.097) or multivariate analysis. The study demonstrates an association between maternal CMD and infant growth impairment in rural sub-Saharan Africa.