The present study investigated whether combined ingestion of green tea catechins (GTC) and monoglucosyl hesperidin (GHES) influences the pharmacokinetic parameters of polyphenols and serum triglycerides (TG). We conducted 2 randomized, controlled trials. Study 1: 8 healthy male subjects participated in a crossover study in which they ingested a test beverage containing GHES (0, 84, 168, or 336 mg GHES) with GTC, or 336 mg GHES without GTC. After ingestion, the pharmacokinetic changes in plasma hesperetin (HEP) and catechins were measured. Study 2: 36 healthy male and female subjects (mean age, 53 ± 2 years; mean BMI, 25.2 ± 0.5 kg m-2) were recruited for a double-blind, placebo-controlled study in which they ingested a test beverage containing 165 mg GHES with 387 mg GTC or a placebo beverage daily for 4 weeks. Fasting serum TG and other lipids and glucose metabolites were analyzed. Study 1 showed that the pharmacokinetics of HEP did not differ significantly between the 336 mg GHES without GTC treatment and the 168 mg GHES with GTC treatment. Study 2 showed that continuous ingestion of 165 mg GHES and 387 mg GTC for 4 weeks significantly decreased fasting serum TG levels compared with baseline values (change in TG, -30 ± 13 mg dl-1, P = 0.040) in the intention-to-treat analysis. In conclusion, our findings suggest that GTC affects the oral bioavailability of GHES, and combined ingestion of low doses of GHES with GTC effectively improves fasting TG levels.