Background: Primary immunodeficiency diseases (PIDs) refers to genetic conditions that are typically distinguished by weakened host defense and a higher susceptibility to infection. Objective: This study aims to spotlights on PIDs syndromes among patients attending Mansoura University Children's Hospital to achieve early detection, proper diagnosis and better outcome. Patients and methods: A cross-sectional retrospective study was conducted to include all patients diagnosed as PID according to hospital registrations since 2014 till December 2020. Patients with confirmed diagnosis of PIDs based on suggestive clinical diagnosis plus basic immunologic work up were included in our study. Results: The median age of onset was 9 months, the median age at diagnosis was 24 months, and the median diagnosis lag was 12 months among 158 cases, including 105 (66.5%) men and 53 (33.5%) women. The male-to-female ratio was 1.9:1. Results revealed that PIDs is common between consanguineous parents (58.2%) with positive history of sibling died (15.8%), positive family history of recurrent infections (24.7%) and history of sibling diagnosed as PID (24. 1%). The most common type was primary cellular and combined immunodeficiency (CID) 57 (36.1%) patients with least dominant Disorder of immune dysregulation 1 (0.6%) patient. The most common presentation was recurrent pneumonia (70.6%) of patient and the least sign was family history of PID (8. 2%). Mortality rate was 27.2%. Conclusions: PID was common among consanguineous parents, more common in male than female. The most common type in our study was primary cellular and CID. The most common presentation was pneumonia.