The seroprevalence of Brucella antibodies in the serum of goats and sheep reared on semi-arid pastoral systems of northeastern Mexico was assessed. Additionally, species, gender, and predominant breed were evaluated as risk factors for seropositivity to brucellosis. Data were from 375 herds of goats or co-mingled goats and sheep. Serum samples from 11001 goats and 4741 sheep collected between 2016 and 2019 were analyzed with the brucellosis card test. The disease affected 12% of herds. The overall prevalence of brucellosis seropositivity in goats and sheep were estimated at 2.1% (95% CI = 1.78-2.31) and 0.8% (95% CI = 0.58-1.10), respectively. Brucellosis seropositivity was two times more likely (p < 0.01) in goats than sheep. The risk of seropositivity to brucellosis for goats and sheep was 2.3 and 3.2 times higher (p < 0.01) in females than in males. Toggenburg goats were more likely (p < 0.01) to be seropositive to brucellosis than all other breeds of goats. In contrast, criollo sheep were more likely to be seropositive to brucellosis than hair sheep composite breeds. The current study revealed that brucellosis is not widely distributed in the study area, despite the absence of Brucella vaccination programs in recent years. Also, of all animals screened, seropositivity to Brucella infection was highest in Toggenburg compared to other dairy and meat breeds; Criollo sheep also presented the highest seropositivity to brucellosis compared to hair sheep composite breeds. Finally, females compared to males had increased odds of testing positive for brucellosis.