A cross-sectional study was conducted from April 2013 to September 2013 to determine the seroprevalence and possible risk factors for human Toxplasma gondii infection in East Hararghe Zone, Ethiopia. Serum samples were analysed using direct agglutination test, and immunosorbent agglutination assay for detecting IgG (n = 354) and IgM (n = 167) T. gondii antibodies. The T. gondii IgG and IgM seroprevalences were 65·8% [95% confidence interval (CI) 60·62–70·75] and 8·98% (95% CI 5·11–14·38), respectively. Gender difference in IgG seroprevalence was not significant (P > 0·05), but 69·5% of adults exhibited an IgG seroresponse to T. gondii. Pregnant women showed 76·4% and 9·3% seropositivity to IgG and IgM antibodies, respectively. Multivariable logistic regression analysis identified the risk factors significantly associated with T. gondii seropositivity were district [odds ratio (OR) 2·24, 95% CI 1·25–4·01, P = 0·007], pipe water source (OR 6·70, 95% CI 2·70–16·64, P < 0·001), age, with adults (OR 4·32, 95% CI 1·91–9·75, P < 0·001), and keeping cats in the home (OR 2·01, 95% CI 1·11–3·65, P = 0·021). The high seroprevalence of toxoplasmosis in the human population in the study area and the corresponding level of IgM seropositivity may be indicative of reactivation or recent infection and further studies on the status of congenital toxoplasmosis in the study area merit consideration.