Background: To highlight the heterogeneity of acute temporal blood pressure (BP) changes in the ATACH-2 trial (Antihypertensive Treatment of Acute Cerebral Hemorrhage-2) and associations with the outcomes of intracerebral hemorrhage. Methods: One thousand patients with acute intracerebral hemorrhage, who had been randomized to intensive (110–139 mm Hg) or standard (140–179 mm Hg) systolic BP (SBP) lowering with intravenous nicardipine in ATACH-2 from 2011 to 2015, were analyzed about temporal changes in hourly maximum SBP up to 24 hours after randomization using group-based trajectory modeling. Outcomes included death or disability (modified Rankin Scale score 4–6) at 3 months, neurological deterioration within 24 hours (≥2-point decrease in Glasgow Coma Scale score or ≥4-point increase in National Institutes of Health Stroke Scale score), and acute kidney injury (≥0.3 mg/dL within 48 hours or ≥1.5-fold increase in serum creatinine) within 7 days after onset. Results: Group-based trajectory modeling revealed 4 SBP trajectory groups: moderate SBP (from ≈190 mm Hg at hospital arrival to 150–160 mm Hg after randomization; n=298), moderate-to-low SBP (from ≈190 mm Hg to <140 mm Hg; n=395), high-to-low SBP (from >210 mm Hg to <140 mm Hg; n=134), and high SBP (from >210 mm Hg to 160–170 mm Hg; n=173). Patients with intensive treatment accounted for 11.1%, 88.6%, 85.1%, and 1.7% of each group, respectively. Compared with the moderate-to-low SBP group, the high-to-low SBP group showed increased risks of death or disability at 3 months (adjusted odds ratio, 2.29 [95% CI, 1.24–4.26]) and acute kidney injury (adjusted odds ratio, 3.50 [95% CI, 1.83–6.69]), while no increase in neurological deterioration was seen in this group (adjusted odds ratio, 0.48 [95% CI, 0.20–1.13]). The moderate SBP and high SBP groups showed no significant risk differences for such outcomes. Conclusions: Data-driven observation using a group-based trajectory modeling approach may be useful to clarify the relationship between antihypertensive treatment, temporal SBP changes, and outcomes in acute intracerebral hemorrhage. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01176565.