Silver nanoparticles (SNPs) are widely invested in nanomedicine and consuming products due to their unique antimicrobial properties. However, little is known about the toxicity of these particles on human health. The present investigation was carried out to investigate the histological alterations induced in the lung tissues by 20±5 nm SNPs. Male albino Wistar rats were exposed to SNPs at a daily dose of 2 mg/kg for 21 days. Lung biopsies from all rats under study were subjected to histopathological examinations. Exposure to 20±5 nm SNPs induced the following pulmonary alterations: thickened alveolar wall, macrophages invasion and inflammatory cells infiltration, lymphatic follicles enlargement, pulmonary edema, alveolar hypersensitivity and interstitial congestion. Occasional atelectasis and fibrocytes proliferation were also detected. The findings of the present work might indicate that SNPs potentially trigger oxidative stress and alterations in the pulmonary tissues that may affect the function of the lungs.