Toxoplasma gondii and Bartonella spp. are zoonotic pathogens of cats. In the present study, the prevalence of antibodies to T. gondii and Bartonella spp. were determined in sera from 210 domestic cats from Bensalem, Pennsylvania. Using a modified agglutination test, antibodies to T. gondii were found in 41 (19.5%) of the 210 cats with titers of 1:25 in 4, 1:50 in 9, 1:100 in 7, 1:200 in 3, 1:400 in 3, 1:800 in 5, 1:1,600 in 4, and 1:3,200 or higher in 6. For T. gondii, seroprevalence increased with age of the cat: 15 of 113 (13.2 %) were seropositive compared with 26 of 97 (26.7%) older than 11 mo. Of these 210 cats, 54 (25.7%) were positive for Bartonella spp. antibodies, with titers of 1:64 in 20, 1:128 in 21, 1:256 in 9, and 1:512 in 4. Seventeen cats had antibodies to both organisms. There was no correlation between T. gondii and Bartonella spp. seropositivity. Overall the seroprevalence of T. gondii antibodies in cats in this population is much lower compared with those reported in other localities in the United States and other countries.