A survey of the micro-land snails in the mountain rainforest or “Yungas” of Tucumán Province, Northwestern Argentina (26°20′–27°30′S) was carried out. A total of 75 samples were processed from 25 stations of 10 × 10 m each. We identified the snails collected to species level and built a species per station data matrix to analyze patterns of diversity. Non-parametric estimators (ICE and Chao2) using EstimateS 5.0.1 were used to estimate the true diversity of the area, the degree of undersampling, and spatial aggregation in the data. Other diversity measurements such as Shannon and Whittaker indices were also calculated. Our study estimated the micro-mollusc species richness of the Yungas of Tucumán to be 21 species distributed among 9 families, with a notably high number of specimens collected (7741). The most speciose family was Charopidae with a total of seven species identified. However, the most abundant families were Diplommatinidae and Systrophiidae. Adelopoma tucma and Wayampia trochilioneides were the most abundant species, the least frequently found species was Lilloiconcha tucumana. The non-parametric estimators showed that our survey was complete and that patchiness did not affect diversity estimations. San Javier and Escaba stations had the highest species richness, the most diverse station was Escaba. Most previous studies in other places in the world show high species richness and low density of specimens. In Tucumán, on the contrary, the absolute abundance of specimens was high with a low species richness.