Maternal intake has a role in the composition of nutritional content, especially breast milk protein, but is rarely studied in fish producing areas (coastal). This study aimed to assess protein concentrations in human milk and evaluate their changes according to diet. The type of study was analytical observation, cross-sectional research design with a total sample of 50 from 313 breastfeeding mothers of infants 0-6 months domiciled at the Padang Serai Health Center. Dietary intake is collected using the food recall form 2 x 24 hours. Breast milk is collected in the morning as much as 30 ml using an electric breast pump. T-Test Independent analyzed the data. The results showed that as many as 10% of mothers had breast milk protein content above 0.9 g/100mL, and there was a relationship between maternal age, energy, and protein with breast milk protein content. Maternal diet, especially energy and protein, affects the protein content of breast milk. It is recommended that mothers improve their daily intake through nutritionally balanced and varied foods.