ABSTRACT Daily activity patterns are important elements of species behavior that reflect how they interact with their environment and with other related species. To investigate these patterns is crucial to understand how environmental or community changes may affect this behavior in each particular species. Within the Felidae family, research becomes fundamental to assess how small wild cats respond to local conditions and pressures, once there is a large gap in studies addressing such issues. Leopardus guttulus (Hensel, 1872) is an endangered species classified as Vulnerable (VU) at a regional and global level, being threatened mainly by the loss and fragmentation of its habitats. The aim of this study is to document the daily activity patterns of L. guttulus at the Lami Biological Reserve, and the influence of seasonality and temperature on those patterns. We also aimed to quantify how many individuals were using the Biological Reserve during the study period and evaluate their permanence in the area. We obtained 25 independent records for L. guttulus, which was the only cat species recorded at the site during the study period. In general, the species presented a cathemeral habit, being active throughout the 24 hours of the day, but with a more crepuscular/nocturnal activity in the spring and summer. The relationship between the species’ activity and temperature showed that more than 70% of the records were obtained in a narrow range of 10-17°C. We identified at least two individuals that remained at the site from four to six months of the year, with a higher detection frequency between August and November. Our results showed some interesting trends for the temporal activity of L. guttulus, suggesting flexibility related to seasonality, and the importance of the biological reserve to the preservation of this cat species in the southern limit of its distribution.