Although several large trials that included African American patients with hypertension have demonstrated the superiority of diuretics as an initial monotherapy, its applicability to other ethnicities remains questionable. The purpose of this study was to investigate whether diuretics as first-line antihypertensive medications are superior to other classes of drugs in the Korean population. Using the Korean National Health Insurance Service database, we analyzed 95,201 Korean hypertensive patients without prior history of cardiovascular disease who started a single antihypertensive drug between January 2002 and December 2017. The primary endpoint was a composite of cardiovascular death, myocardial infarction and stroke. Each endpoint was compared among five classes of antihypertensive drugs [diuretics, angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), and beta-blockers (BBs)]. In multivariable Cox analysis, diuretics were superior to ACEIs (hazard ratio [HR], 1.58-2.01), inferior to ARBs (HR, 0.37-0.43) and similar to CCBs and BBs for the primary endpoint. Similar findings were obtained for all-cause and cardiovascular mortality and stroke. This result was consistently observed in the longer treatment group and in the propensity score-matched pairs. In Korean hypertensive patients without cardiovascular disease, initiation with diuretics could not be superior to other medications, but rather inferior to ARBs in preventing adverse cardiovascular outcomes. Randomized studies are needed to confirm our results.