Anaplasma platys is an obligate intracellular gram-negative bacteria forming morulae in platelets. Reports of infection in cats are quite recent and scarce, especially in Brazil. The aim of the present study was to detect domestic cats naturally infected by A. platys, as well as evaluate hematological changes associated to the infection. Blood samples from 219 domestic cats from the metropolitan region of the state of Rio de Janeiro were collected. The molecular detection of A. platys was performed by real-time PCR (qPCR) using the TaqMan system with target to the gltA gene. Positive samples were subjected to nested PCR (16S rRNA), and subsequently sequenced. Hematological evaluation and direct microscopic examination were also performed. Eight animals were positive in qPCR for A. platys, and the average value Cq of positive samples ranged from 32 to 36 cycles. Of these, only two cats were positive in nested PCR and sequencing showed 100% similarity with A. platys in GenBank. Platelet inclusions were observed in 17 animals. However, morphological changes, inclusions of other agents such as Ehrlichia canis, and technical artifacts are possible differential diagnoses for these inclusions. The most common hematologic disorder observed in positive animals was thrombocytopenia. The results of this study demonstrate the presence of A. platys in the cat population of Rio de Janeiro, serving as a warning to veterinarians about this possible diagnosis. In addition, this is the first detection and molecular characterization of A. platys in the city of Rio de Janeiro.