BACKGROUND: Peste des petitis (PPR) is a highly contagious viral disease with high incidence and mortality rate, which is endemic in the Middle East, Southwest Asia, and Africa. This disease has been causing economic losses in sheep and goat flocks in these areas. Studies have shown that environmental and host risk factors can influence the severity of PPR infection. OBJECTIVES: We conducted the present study to investigate the prevalence of PPR in small ruminants population of Garmsar city and its suburbs. Furthermore, the effect of host factors, including animal species, gender, and age, and environmental factors, such as sampling season, geographical area, and sampling location, were evaluated. METHODS: Blood samples of 180 sheep and goats were taken in spring, summer, and autumn and after centrifugation, serum samples were isolated. We measured antibody response using competitive enzyme linked immunosorbent assay (C-ELISA). RESULTS: The apparent and true prevalence of contamination in small ruminants of Garmsar and its suburbs ware 24.44 % and 23.91 %, respectively. The results revealed non significant relationships between animal species (p < /em>= 0.08), gender (p < /em>= 0.14), and age (p < /em>= 0.98) with PPR serum prevalence. Meanwhile, there was a significant relationship between season (p < /em>= 0.03), geographical area (p < /em>= 0.0004), and sampling location (p < /em>= 0.0001). In addition, the odds ratio of PPRV infection in autumn was 2.62 (95% CI: 0.06 – 6.02; p < /em>< 0.05) times more than that of other season and in the south-eastern of Garmsar, it was 6.71 (95% CI: 3.01-17.60; p < /em>< 0.05) times more than that of other geographical regions. The odds ratio of PPRV infection in the Mahmood Abad village was 63.63 (95 % CI: 12.14 – 132.93; p < /em>< 0.05) times higher than that of other villages. CONCLUSIONS: According to the obtained findings, PPR was proven to be an endemic disease in Garmsar and its suburbs and the environmental risk factors have a greater impact on the seroprevalence of disease than host risk factors. Therefore, in order to control the disease in endemic areas, further attention should be paid to environmental risk factors and minimizing the risk of epidemics through vaccination at sensitive timescales and areas before high-risk environment changes.