Background: Childhood-onset systemic lupus erythematosus is a multisystem, autoimmune disease, beginning before the age of 18 that may affect any organ system. The aim of the study was to assess the role of spirometery in detection of pulmonary involvement in children with lupus nephritis and to correlate spirometric parameters with degree of renal affection. Patient and Methods: This cross-sectional study was conducted in Nephrology unite at Zagazig University Hospital on 24 cases that diagnosed SLE patients during the period from Oct 2019- Mar 2020. Patients in the study had subjected to complete history taking, Laboratory investigations included hematological and examination of urine, kidney function test, Chest X-ray, ultrasonography of chest and Renal Biobsy, pulmonary function test, SLED score. Results: Restrictive lung disease was prevalent in 54.2% of patients, mean value of FEV1 was (86.208 ± 23.268), forced vital capacity was (79.321± 23.79), FEV1/FVC was (108.14±11.731), MEF75 was (88.404±19.703). MEF50 was (93.358±25.616). MEF25 was (107.808±47.54), PEF was (84.4± 18.865) there was statistically significant negative correlation between systemic lupus erythematous Disease score and Forced expiratory Volume in 1 sec, forced vital capacity and forced expiratory flow at 25% FVC There is statistically significant negative correlation between grades of nephropathy by renal biopsy and forced expiratory flow at 25% FVC. Conclusion: Present study showed that pulmonary diseases occur frequently in childhood onset Systemic lupus erythematosus. Serial PFT studies may be useful in assessing the presence of lung involvement in childhood onset SLE and monitoring of course and activity of the disease