Background: Adult-onset seizures are a significant clinical problem with diverse etiologies and variable outcomes. Methods: This hospital-based descriptive study was conducted at No. (2) Military Hospital (500-bedded), Yangon, Myanmar, from January to December 2024. A total of 19 patients aged ≥18 years presenting with new-onset seizures were included. Results: Males predominated (84.2%), with most patients in the 41–60-year age group. EEG findings were normal in 36.8% of cases, while non-epileptiform abnormalities were most common (47.4%). Mesial temporal sclerosis was the leading etiology (26.3%), followed by encephalitis (15.8%). Most patients (89.5%) were discharged, while 10.5% died; all deaths were associated with secondary brain metastasis. Conclusion: Structural brain abnormalities were the predominant cause of adult-onset seizures. Outcomes were generally favorable, except in patients with metastatic disease.