Background and Objectives: The optimal anesthetic technique for carotid endarterectomy (CEA) remains debated. We compared cervical plexus block (cervical plexus block) with general anesthesia (GA), focusing on new-onset atrial fibrillation (NOAF), and explored dexmedetomidine (DEX) sedation during cervical plexus block. Materials and Methods: In this single-center retrospective cohort, 133 CEA procedures (cervical plexus block, n = 83; GA, n = 50) were analyzed; 1:1 propensity score matching yielded 42 pairs. Outcomes included NOAF, 30-day major adverse cardiac and cerebrovascular events (MACCE), mortality, perioperative arterial pressure, vasoactive and analgesic requirements, intensive care unit (ICU) stay, and costs. Results: NOAF occurred in 4.8% of cervical plexus block and 24.0% of GA procedures (p < 0.001; propensity score–adjusted odds ratio 0.11, 95% CI 0.03–0.42) and in 0.0% vs. 23.8% of matched procedures (p = 0.002). In matched pairs, cervical plexus block was associated with a smaller rise in systolic pressure during clamping, less intraoperative dopamine use (9.5% vs. 54.8%), fewer postoperative analgesic requirements (28.6% vs. 73.8%), and a shorter ICU stay (median 12.0 vs. 24.0 h; all p < 0.01). Stroke, MACCE, mortality, and total costs did not differ. Within the cervical plexus block group, DEX was associated with less additional intraoperative analgesia (16.3% vs. 58.8%; p < 0.001) and less NOAF (0.0% vs. 11.8%; p = 0.025). Conclusions: cervical plexus block was associated with less NOAF, more stable intraoperative arterial pressure, lower vasoactive and analgesic requirements, and a shorter ICU stay than GA, without higher costs. The exploratory association of DEX with less NOAF warrants confirmation in prospective studies.