Mycoplasma synoviae (MS) is a key avian pathogen that causes respiratory, joint, and reproductive issues in poultry, resulting in significant economic losses. This study aimed to determine the seroprevalence and pathological changes linked to MS infection in commercial broiler flocks in District Karak, Khyber Pakhtunkhwa, Pakistan. A total of 200 blood samples were collected from 13 broiler farms and tested using an indirect ELISA kit to detect MS-specific antibodies. Additionally, tissue samples from the trachea and lungs were taken from naturally infected birds and examined histopathologically. The serological results showed that 41 out of 200 samples (20.5%) tested positive for MS antibodies, indicating moderate pathogen circulation in the area. Risk factor analysis revealed higher seroprevalence in birds over three weeks old (23%) compared to those under three weeks (12%), and in smaller flocks (<2000 birds; 25%) versus larger flocks (>2000 birds; 19%). However, statistical analysis (Chi-square test) found no significant associations (p > 0.05) with age, flock size, feed, or mortality. Clinical signs like respiratory distress, anorexia, ascites, and white diarrhea were weakly linked to seropositivity. Gross lesions included tracheal hemorrhages, splenomegaly, synovitis, and lung consolidation. Histopathology showed epithelial desquamation, leukocytic infiltration, hemorrhage in the trachea, and alveolar septal thickening and congestion in the lungs, consistent with septicemia progression of MS infection. This study confirms that Mycoplasma synoviae is endemic in broiler flocks of District Karak, with characteristic respiratory lesions. The findings highlight the importance of regular surveillance, biosecurity, and improved diagnostic methods to reduce the impact of MS on poultry production in Pakistan.