The seroprevalence study for leptospirosis in bovines and humans was realized in family holder farms along the Transamazon Highway. The prevalence of bovine leptospirosis was 97% [90.9 - 99.5%] of farms with at least one positive animal according to microscopic agglutination test for the leptospirosis diagnostic. In 61.2% of the tested herds, the serovar hardjo was the most common, followed by the serovar bratislava (9%) and the serovar shermani (4.5%). The serologic prevalence of leptospirosis in humans was 32.8% [23.4 - 43.5%] in family groups with at least one positive individual according to microscopic agglutination test for the leptospirosis diagnostic. In 9% of family groups, the serovar bratislava was the most common, while serovar hardjo and grippotyphosa accounted for 6% and 4.5%, respectively. The impact of these results is discussed in relation to animal production and public health. Suggestions have been proposed in order to improve the situation in the region.