Background: Inborn errors of metabolism are a heterogeneous group of disorders that have many sequels. Mothers of these children are living various experiences which need many studies and explanations. The aim of the study: This study aimed to explore the lived experiences of mothers caring for children with some inborn errors of metabolism like phenylketonuria, gauche disease, and mucopolysaccharidoses. Methods: Interpretive phenomenological analysis using Braun & Clarke approach that provides a six- phase guide and data were gathered using semi-structured interviews and the interviews were audio recorded. Setting: The study was conducted at the Pediatric Metabolic, and Genetic Unit at Zagazig University Hospitals. Participants:A purposive sample composed of 21 mothers whose children suffer from (10 Phenylketonuria, 5 Mucopolysaccharidoses, and 6 Gaucher Disease). Results: The six final themes were revealed from exploring mothers' experiences including the complexity of the diagnosis process, seeking understanding, coping with the disease effects, perceived social support, concerns for the future, and access to the health care services. Conclusion: Inborn errors of metabolism had heavy social, psychological, and financial burdens on all family members. However, this study found that mothers were most affected by psychological issues, particularly isolation. Recommendation: it is become essential to develop programs for helping mothers of children with inborn errors of metabolism to reduce the burden of these diseases on mothers and consequently the children and the whole family