Background and rationale: Acute otitis externa is a disease that significantly affects the life and health of people, mostly caused by bacteria, fungi, virus and irritation from chemicals. Besides that, it can also be caused by trauma such as ear picking, spinning ears, swimmer’s ear and wiping the ear too hard, and if not treated in time serious complications are possible. Objective: To study the risk factors associated with acute otitis externa at the ENT Department, Mahosot Hospital. Methodology: This study was cross-sectional, descriptive study among patients with ear-ache and acute otitis externa. Data were collected by using questionnaire interviewed face to face and by ear examination. The data were entered into Epi-data and analyzed by using SPSS software. Results: Of 186 participants, 62.9% had otitis externa, with a mean (95%CI) age of 32 (01-76) years. The commonest age group was those aged less than 15 years old with 29%. Males were 1.88 times more likely to present with otitis externa than females. Occupational groups at risk of disease are farmers/laborers/ housewife/others and those living in rural areas was 2.7 times having acute otitis externa. Those who had swum or had travelled in the forest and ear picking had a higher frequency of acute otitis externa (1.6 times) and patients who regularly cleaned their ears with a cotton swab were 1.39 times of having otitis externa and some patients who used hair clip for ear picking had a higher frequency of acute otitis externa (2.44 times). Conclusion Most of patients have common clinical manifestations of which are tinnitus, earache, swelling or redness of the ears, hearing loss and itching. Demographic characteristics, history, and ear health care behaviors are associated with acute otitis external.