Objectives. To determine the seroprevalence of brucellosis and leptospirosis in pigs reared on small-scale farms in rural areas of the district of Tandil, Buenos Aires Province, Argentina; to analyse the associated risk factors; to describe the prevalent Leptospira spp. serogroups; and to determine the spatial distribution of both diseases. Materials and methods. A total of 340 serum samples were obtained. Buffer Plate Agglutination Test, Rose Bengal Test, and Fluorescence Polarisation Assay were used to detect antibodies against Brucella spp. Microscopic Agglutination Test was applied for serological diagnosis of leptospirosis. Statistical methods were used to evaluate the factors associated with the infections. Results. Seroprevalence of 0% and 22.6% was observed for brucellosis and leptospirosis, respectively. The most prevalent Leptospira serogroups identified were Canicola, Ballum, Icterohaemorrhagiae and Pomona. The main risk factors associated with leptospirosis infection were farms with a higher number of pigs and the presence of horses and wild boars near or within the farms. The use of milling by-products of cereal grains as animal feed and the presence of weaning cages were also associated. A relevant spatial cluster of seropositivity to Leptospira spp. was identified in a low-altitude area. Conclusions. Our results suggest that brucellosis is probably controlled, but Leptospira spp. are present in the farming systems under study. Knowledge of brucellosis and leptospirosis seroprevalence, spatial distribution and associated risk factors can be useful for the prevention and control of endemic zoonotic diseases in the region.