Canine cardiac dirofilariasis is a parasitic zoonotic disease caused by Dirofilaria immitis. This research work is aimed to find out the prevalence of both a microfilaremic (patent infection) and occult forms (amicrofilaremic form) of cardiac dirofilariasis in stray and police dogs of Nineveh governorate (in northwestern Iraq). From October 2021 to January 2022, the blood of ninety dogs of various breeds, including 45 local breeds stray dogs and 45 police dogs, mostly of Belgian Malinois and German Shepherd breeds, with an age range of 1 to 11 years (median: 4.5 years), were examined microscopically by wet mount, acridine orange stained blood smears and modified Knott's test to detect circulating microfilaria. All the samples were further tested by a commercial antigen- enzyme-linked immune sorbent assays kit (Heartworm Ag ELISA kit, Canine, DRG International Inc., USA) in order to detect dogs with occult cardiac dirofilariasis. A total of 49 samples were microfilaria positive, giving a prevalence value of 54.4%. D.immitis antigens were detected in 27.8% of the examined sera, with an overall prevalence of 78.9%. Stray dogs showed a higher prevalence for both microfilaremia and occult forms of cardiac dirofilariasis compared to police dogs in Nineveh Governorate of Iraq. The agreement between the modified Knott's test (Gold standard) and wet mount, acridine orange stained blood smears, and Ag ELISA using Cohen’s Kappa index was light for the wet mount (0.030) and substantial for Ag ELISA(0.462), and acridine orange stained blood smears (0.607). The findings of the present study provide evidence for the prevalence and pattern of canine cardiac dirofilariosis in dogs (both stray and police) in Iraq’s Nineveh Governorate, requiring a phylogenetic analysis.