Background: Hemorrhagic transformation (HT) is a major complication of intravenous thrombolysis in acute ischemic stroke (AIS). While an elevated heart rate (HR) at admission is linked to poor outcomes, the heart rate trajectory (HRT) may offer a better prognostic value. This study investigated the association between 24-hour HRT patterns and HT in patients treated with intravenous thrombolysis for AIS. Methods: This retrospective cohort study included patients with AIS who received intravenous recombinant tissue plasminogen activator between January 2015 and February 2025. Patients aged ≥18 years with AIS, complete 24-hour HR data, and follow-up neuroimaging data were analyzed. Latent mixture modeling was applied to classify the HRT patterns using hourly HR measurements. The primary outcome was HT, and the secondary outcomes were in-hospital mortality and modified Rankin Scale (mRS) score at discharge. Results: Among the 164 patients with AIS, 38 (23.2%) developed HT. Four distinct HRT patterns were identified: low-early decline (7.3%), moderate-gradual decline (37.8%), moderate-stable (40.9%), and high-gradual rise (14.0%). Compared with the low-early decline HR group, the high-gradual rise HR group showed a significantly increased risk of HT (adjusted odds ratio, 11.1; 95% CI, 1.0–122.6; P=0.049). In-hospital mortality did not differ significantly, but the discharge mRS scores were significantly higher in the moderate-stable group than in the low-early decline group (P=0.010). Conclusion Distinct 24-hour HRT patterns were associated with HT and discharge outcomes. A persistently high HR may serve as an early risk marker and therapeutic target.