not-yet-known not-yet-known not-yet-known unknown INTRODUCTION Leptospirosis, a neglected tropical disease (NTD), poses a significant public health threat globally, including in sub-Saharan Africa, where it disproportionately affects low-income populations in rural areas.(Allan et al., 2015) . Caused by the pathogenic spirochete from the genus Leptospira , the disease is particularly concerning in environments with high human-livestock-wildlife interaction. (Vijayachari et al ., 2008; Torgerson et al ., 2015). It is estimated that severe human cases between 300,000 and 500,000 occur annually, with a mortality rate of up to 30% (Costa et al ., 2015). Approximately, 58,900 human deaths are reported annually. (Costa et al ., 2015). According to Allan et al . (2015), acute human leptospirosis has been recorded in 18 African nations, including Tanzania. Rodents, especially, serve as primary reservoirs, transmitting the disease to humans and animals through contaminated water or soil. (Boey et al. , 2019). Tanzania is regarded as one of many favorable environments for establishing Leptospira because it is  a tropical country. (Masunga et al ., 2022). In recent years, sub-Saharan African countries, including Tanzania have experienced periodic outbreaks of human and animal leptospirosis in many regions, the most recent being human leptospirosis (Mgunda in Swahili) in Ruangwa, Lindi, whereby three deaths and twenty confirmed cases were reported. (Masunga et al ., 2022). Despite its global presence, the disease is poorly studied in many regions, including Tanzania, which is highly vulnerable due to its tropical climate and extensive agricultural and livestock activities. (Mlowe et al ., 2023). Domestic animals such as cattle serve as maintenance hosts of the Leptospira interrogans and potential incident hosts of the spirochetes. (Ellis, 2015). Clinical signs of acute bovine leptospirosis include jaundice, high fever, hemoglobinuria, and renal damage. Leptospires cause abortion, neonatal, and stillbirths in pregnant cows (Ellis, 2015). Previous studies on leptospirosis in Tanzania have primarily focused on cattle, leaving significant gaps in understanding the zoonotic cycle between rodents, humans, and cattle. Recent outbreaks, such as the one in Ruangwa, Lindi, underscore the need for comprehensive studies, especially considering that nearly 70% of Tanzania’s population is engaged in high-risk activities such as farming and livestock keeping. (Motto et al., 2023; Schoonman & Swai, 2009; Swai & Schoonman, 2012a). This study aimed to determine the seroprevalence of leptospirosis in rodents, cattle, and humans in Muheza District, Tanzania, and to identify potential risk factors, using a One Health approach to assess transmission dynamics among these groups.