Abstract Background: Interstitial lung diseases impair gas exchange resulting in exertional dyspnea and reduced lung function which limit daily activities and impair quality of life. All these changes are related to respiratory muscles dysfunction. Aim of Study: To investigate the effect of inspiratory muscles training on ventilatory function and functional capacity in patients with Interstitial lung diseases. Material and Methods: Thirty female patients with inter-stitial lung diseases with mean of age of ±48.57 were recruited from outpatient clinic of Beni Seuf University Hospital. The study lasted from July 2018 to August 2019. Patients received threshold inspiratory muscles training for 8 successive weeks, 3 sessions/week. The outcome measures were Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1/FVC ratio, Maximum Ventilatory Ventilation (MVV) and the distance walked in 2min which were measured before and after the intervention. Results: A significant increase were found from pre to post intervention in FVC (0.0001), FEV1 (0.0001), MVV (0.001) and the distance walked in 2min walk test (0.0001) while a non significant difference was found in FEV1/FVC ratio (0.09). Conclusion: Based on the results it can be concluded that inspiratory muscles training can be adjunctive to the rehabil-itation program for patients with ILD aiming for improving their ventilatory function and functional capacity.