Background: Limited knowledge of antihypertensive treatment of the elderly potentially impedes effective strategies for hypertension management in this growing patient group. We aimed to investigate temporal trends for first-line drug choice for antihypertensive treatment and treatment continuity among patients ≥75 years from 2000 to 2021. Methods: Using nationwide Danish registers, patients ≥75 years initiated for the first time on antihypertensive drugs: Angiotensin converting enzyme inhibitors (ACEi), angiotensin II receptor blockers (ARB), beta blockers (BB), calcium channel blockers (CCB), thiazides, or combinations, were identified. Patients with other indications than hypertension were excluded. Treatment continuity was described using claimed prescriptions the first 180 days following study entry. Results: From 2000 to 2021, 170,769 patients (median age 80 years [interquartile range:77–84], 60.3% female) were included. From 2000 to 2003 to 2015–2021 the proportion of first-line drug choice increased for ACEi (8.7% to 14.9%), ARB (4.1% to 23.9%), and CCB (10.7% to 27.6%), decreased for thiazides (60.6% to 15.9%) and remained stable for BB (12.9% to 14.1%) and combinations (2.9% to 3.6%). For 157,457 patients alive after 180 days, discontinuation was highest among patients initiated on thiazides (28.3%) whereas most patients continued the same single drug regimen if they started on ACEi (55.2%), ARB (65.0%), BB (57.2%) or CCB (59.3%). Conclusions: From 2000 to 2021 thiazides have been replaced by ACEi, ARB and CCB. Thiazides had the lowest treatment continuity while ARB appeared preferred slightly over ACEi. Differences in adherence in relation to first-line drug choice may warrant scrutiny regarding recommendations for the elderly.