The study determined the seroprevalence of S. gallinarum infection in free-range chickens in Nasarawa State, Nigeria. A total of 2772 serum samples collected from free-range chickens in 12 selected villages/towns in Nasarawa State were screened for specific antibodies against S. gallinarum by the rapid serum agglutination method. Overall, 236 (8.5%) of the chickens had detectable antibodies against S. gallinarum. Nasarawa South Senatorial Zone had a significantly higher (p<0.05) antibody prevalence of 109 (9.5%) when compared with Nasarawa North, 59 (8.5%) and Nasarawa West, 68 (7.2%). There was significant difference (p<0.05) in S. gallinarum antibody prevalence in chickens sampled from individual villages/towns, with Assakio, Keana and Wamba having significantly higher antibody prevalence rates of 17 (21.3%), 21 (21.0%) and 16 (20.0%), respectively. A significant difference (p<0.05) was observed in the prevalence of S. gallinarum antibody in the sampled chickens in relation to age, and prevalence was found to be higher (p<0.05) in the older.birds Thus chickens of age greater than 34 weeks and 28-34 weeks had antibody prevalence of 47 (13.4%) and 57 (10.0%), respectively. S. gallinarum antibody prevalence was significantly higher (p<0.05) in the rainy season (June to October) 126 (10.5%) with the highest infection peak in September, when compared with the dry season (December to May), 110 (7.0%). The layer chickens had a significantly higher (p<0.05) antibody prevalence of 138 (19.1%) compared with cockerel, 60 (5.3%) and pullets, 38 (4.1%).