The social representations of complementary feeding are expected to shape parents' decisions and to provide justification or legitimization for their practices. The aims of the present work were: i) to explore the social representations of complementary feeding in parents and health professionals, ii) to evaluate if the onset of complementary feeding modify social representations in parents, and iii) to compare the representations of parents and pediatricians. Three groups of participants were considered: 170 parents of children who had not started complementary feeding (1-4 months old), 170 parents of children who had started complementary feeding (7-10 months old) and 212 pediatricians. Parents were recruited in health facilities in Montevideo (Uruguay), whereas pediatricians were recruited at the National Pediatrics Conference. Participants were asked to complete a word association task with "the first meals of a baby". All the responses provided by participants were grouped into categories using content analysis. The structure of the social representations was assessed considering the frequency of mention and the average rank of appearance of the categories. Results showed that the social representations of complementary feeding for both parents and pediatricians were extremely narrow and mainly focused on specific foods: puree and a small set of vegetables and fruits. None of the categories showed high frequency of mention and low rank of appearance, indicating that the structure of the social representations did not include any element in the first periphery. According to the theory of social representations, results from the present work suggest that the social representations of complementary feeding for Uruguayan parents and pediatricians are deeply rooted and resistant to change.