Objectives: To determine the presence of protease activated receptor-2 (PAR2) and matriptase proteins and quantify the PAR2 and matriptase mRNA expression in the articular cartilage and synovial membrane of cats with and without osteoarthritis (OA). Methods: A total of 28 articular cartilage samples from adult cats (14 OA and 14 normal), 10 synovial membranes from adult cats (5 OA and 5 normal) and three cartilage samples from 9 week old foetal cats were used. The presence of PAR2 and matriptase in the cartilage and synovial membrane of the adult samples was detected by immunohistochemical (IHC) staining while real-time PCR was used for mRNA expression analyses in all samples. Results: PAR2 was detected (IHC) in all OA and normal articular cartilage and synovial membrane samples but confined to only a few superficial chondrocytes in the normal samples. Matriptase (IHC) was only detected in OA articular cartilage and synovial membrane samples. PAR2 and matriptase mRNA expression were however detected in all cartilage and synovial membrane samples. PAR2 and matriptase mRNA expression levels in OA articular cartilage were 5 (P<0.001) and 3.3 (P<0.001) times higher compared to that of the healthy group respectively. There was no significant difference (P=0.07) in the OA synovial membrane PAR2 and matriptase mRNA expression compared to the normal samples. Conclusions and relevance: Detection of PAR2 and matriptase proteins and gene expression in feline articular tissues is a novel and important finding and supports the hypothesis that serine proteases are involved in the pathogenesis of feline OA. The consistent presence of PAR2 and matriptase protein in the cytoplasm of OA chondrocytes suggests a possible involvement of proteases in cartilage degradation. Further investigations into the PAR2 and matriptase pathobiology could enhance our understanding of the proteolytic cascades in feline OA which might lead to the development of novel therapeutic strategies.