Infants consuming maize-based foods are at a high risk of exposure to fumonisins. This study explored the association between exposure of fumonisins from maize and growth retardation among infants in Tanzania. Mothers of 215 infants consented for their children to participate in this study. We estimated maize intake for each child by twice conducting a 24 h dietary recall and fumonisins level in the maize, using HPLC. Fumonisins exposure for each child was estimated by combining his/her maize intake and the fumonisins level in the maize. Of the infants, 191 consumed maize. The maize consumed by 131 infants contained fumonisins at levels varying from 21 to 3201 μg/kg. Fumonisins exposure in 26 infants exceeded the provisional maximum tolerable daily intake of 2 μg/kg body weight. At 12 months of age, infants exposed to fumonisins intakes above the provisional maximum tolerable daily intake of 2 μg/kg bodyweight were significantly shorter by 1.3 cm and 328 g lighter. It appears that the exposure to fumonisins is associated with growth retardation. This is the first study to report an association between fumonisins exposures and growth retardation.