It is known that silver nanoparticles (Ag NPs) and silver nitrate (AgNO3) have harmful effects on the surrounding animals, which may cause several damages to these animals, whether harmful or beneficial. The aim of the present study is to detect damage caused by Ag NPs and AgNO3 to land slugs Lehmannia nyctelia. In this study, land slugs have been exposed to different concentrations (0.04, 0.08, 0.4, 0.8 g/L) of Ag NPs and AgNO3 for 15 days. Histopathological examinations were performed in each of the following (digestive gland, kidney and gonads). The digestive gland appeared several alterations after exposed to different concentrations (0.04, 0.08, 0.4, 0.8 g/L). A clear change in the shape of the cells was noticed where, cells became more flattened and many cells were damaged. The cavity of each tubule increased in size and filled with some remains of damaged cells and the cells became empty from inside. The histological study of the kidney revealed a deterioration in some cells, widening of the spaces between tubules and an increased in connective tissue size than the normal size. The gonads showed clusters of cells in some places, spermatozoa lost the normal shape of the tail. In conclusion the results indicated that, the Ag NPs and AgNO3 can cause damage in histological structure of internal organs of the slug and may cause harmful effects on the terrestrial organisms.