The aim of present study was to determine the seroprevalence of Dirofilaria immitis in dogs and cats from Riyadh, Saudi Arabia. Blood samples were collected by cephalic and jugular venipuncture from 294 dogs and 190 cats from Riyadh. Serum samples were tested against circulating D. immitis antigen using DiroCHEK®, SYNBIOTICS Corporation, San Diego, CA 92127, USA and anti-D. immitis antibodies using Green Spring D. immitis IgG antibody ELISA test kit, Shenzhen Lvshiyuan Biotechnology Co., Ltd. Guangdong, China. D. immitis antigens were detected in 7.82% of the dogs and in 1.58% of the cats, while antibodies against D. immitis were detected in 13.61% of the dogs and 2.11% of the cats. In outdoor dogs, antigens of D. immitis were detected in 10.33% while antibodies were detected in 16.85%. A significant difference in the seroprevalence of D. immitis antibodies in dogs was reported in the summer compared to the winter (p< 0.05). There was no significant difference observed in the seroprevalence between males and females dogs. Older dogs (3-6 years) showed higher prevalence of D. immitis antigen compared to younger dogs, in the contrary D. immitis antibody prevalence was higher in younger dogs (1-3 years) compared to old dogs. In cats, the prevalence of D. immitis antigen and antibody was high in males compared to the females, however, the difference was not statistically significant. There was no effect for the season and age in the prevalence of D. immitis in cats.