The insertion of peripheral intravenous catheters (PIVCs) is common for treatment among hospitalized patients. However, this procedure usually fails before the end of therapy because of several complications, including phlebitis. Therefore, this study aimed to determine the incidence and associated factors of phlebitis among patients with PIVC. A prospective cohort study was conducted in one of the hospitals located in East Coast Malaysia. The presence of phlebitis was assessed using the visual infusion phlebitis score checklist. The patients were followed until PIVC removal. A total of 321 data were collected among patients who received a new PIVC in the medical, gynecology, and orthopedic wards. The incidence of phlebitis was 36.1% (n= 116), and 96.6% of which were grade II. Patients aged 60 years (51.5%), men (42.2%), no known phlebitis history (47.4%), and with chronic disease record (46.8%) were determined as the highest percentage with phlebitis. This study demonstrated that age, gender, and chronic diseases were risk factors of developing phlebitis.