Abstract Background Chinese herbal products (CHPs) have been frequently used among patients with chronic diseases including hypertension; however, the co-prescription pattern of herbal formulae and single herbs remain uncharacterized. Thus, this large-scale pharmacoepidemiological study evaluated the frequency and co-prescription pattern of CHPs for treating hypertension in Taiwan from 2003 to 2009. Methods The database of traditional Chinese medicine (TCM) outpatient claims was obtained from the National Health Insurance in Taiwan. Patients with hypertension during study period were defined according to diagnostic codes in the International Classification of Disease Ninth Revision, Clinical Modification. The frequencies and percentages of herbal formula and single herb prescriptions for hypertension were analyzed. We also applied association rules to evaluate the CHPs co-prescription patterns. Results The hypertension cohort included 154,083 patients, 123,240 patients of which (approximately 80 %) had used TCM at least once. In total, 81,582 visits involving CHP prescriptions were hypertension related; Tian-Ma-Gou-Teng-Yin and Dan Shen (Radix Salvia Miltiorrhizae) were the most frequently prescribed herbal formula and single herb, respectively, for treating hypertension. Conclusions This study elucidated the utilization pattern of CHPs for treating hypertension. Future studies on the efficacy and safety of these CHPs and on drug–herb interactions are warranted.