Objective: The purpose of this study was to clarify the factors related to gemcitabine (GEM)-induced phlebitis. Methods: We retrospectively analyzed 400 cases of intravenous GEM administration to 50 patients from June 2014 to May 2015. We assessed the relationship between GEM-induced phlebitis and various factors including age, sex, BMI, analgesic use (NSAIDs or opioids), and GEM-administration procedures including drug formulation, dosage, and access site. Results: Phlebitis occurred in 79 cases (19.8%). Multivariate analysis indicated that sex (female), age (<65 years old), BMI (≥25 kg/m2; obesity), drug formulation (liquid), and access site (dorsal hand vein) were significantly related to the presence of phlebitis. Discussion: GEM-administration procedures should be modified in patients with these risk factors. It is desirable to apply hot fomentation and to puncture at the brachial region or cubital fossae region vein to prevent phlebitis.