Maternal and child nutrition during the first 1000 days of life is critical in shaping the child's future health outcomes. However, Filipino adolescents have been reported to have highly inadequate nutrient intakes, with pregnancy during adolescence exacerbating the inadequacy due to competing fetal growth and needs. With this, the study sought to evaluate the knowledge, attitudes, and practices (KAP) of teenage mothers on the first 1000 days of life of their children. The child’s height and weight were used to determine the nutritional status of the children based on the WHO Child Growth Standard indices. The level of KAP of the teenage mothers, on the other hand, were determined using a modified questionnaire based from the Food and Agriculture Organization’s Guidelines for assessing nutrition-related Knowledge, Attitudes and Practices. To analyse the results, Spearman Rank-Order Correlation Analysis and Pearson's Correlation coefficient were utilized to determine the association between the level of KAP and the child's nutritional status, as well as the relationship between the level of KAP and the first 1000 days of life, respectively. The findings showed that the teenage mothers were unable to finish high school or enrol in college, and were found to be unemployed and reliant on their parents. Moreover, while the majority had normal nutritional status, there was a medium prevalence of both underweight and overweight, and a very high prevalence of wasting, indicating that the severity of malnutrition situation is critical. Meanwhile, the level of KAP of mothers were found to be low, and that immediate nutrition education intervention to improve their KAP should be urgent based on the cut-off points of FAO. Furthermore, the study discovered that there is no significant correlation between the knowledge, attitude, and practices and nutritional status of the child. However, it was found out that there is a moderate positive relationship between knowledge and attitude, implying that an increase in knowledge would indicate an increase in attitude.