Background <p>Leishmaniosis is a vector-borne disease caused by <i>Leishmania</i> parasites transmitted by infected phlebotomine sand flies. In the epidemiological study reported here, we investigated exposure to <i>Leishmania infantum</i> in sheep (<i>Ovis aries</i>) and goats (<i>Capra hircus</i>) in mainland Portugal.</p> Methods <p>A cross-sectional serosurvey was conducted in three geographical regions of Portugal (Trás-os-Montes, Centre and South), with sampling in 19 municipalities and 87 localities.</p> Results <p>A total of 2124 small ruminants were tested (1820 sheep and 304 goats). Overall seroprevalence was 21.3% (453/2124; 95% confidence interval [CI] 19.6–23.1), with higher seropositivity in sheep than goats (22.4% vs 15.1%). Univariable analysis showed that ruminant species and reported contact between goats and sheep were statistically associated with seropositivity, but these associations were not detected in the subset of 1851 animals used for multivariable modelling. Rather, multivariable logistic regression analysis (<i>n</i> = 1851) showed that several management and biosecurity factors were linked to an increased risk of infection. Increased odds of infection were observed in non-autochthonous breeds (odds ratio [OR] 2.163), holdings without goat–sheep contact (OR 1.920), high aeration/ventilation (OR 1.964), suboptimal drinking fountain hygiene (OR up to 6.221), biannual versus annual disinfection (OR 2.459) and not using equipment from other farms (OR 2.189). Permanent confinement was protective (OR 0.415).</p> Conclusions <p>These results indicate widespread exposure of Portuguese flocks to <i>L. infantum,</i> highlighting the relevance of husbandry practices. Further research is needed to determine whether sheep and goats develop clinical disease and to clarify the implications for animal and public health.</p> Graphical Abstract <p></p>