Human immunodeficiency virus (HIV) tests are commonly performed in emergency departments (EDs) in the United States (US), but the experience and effectiveness of conducting rapid HIV tests in EDs in regions with low HIV seroprevalence outside the US have seldom been reported. An observational cross-sectional opt-in rapid HIV test and counseling program was conducted at an ED in a teaching hospital in Taiwan, a country with low seroprevalence, to determine the acceptance of rapid HIV tests as well as risky behaviors and illness presentations of people who agreed to undergo the tests. Among 7,645 ED patients between 20 and 55 years of age, 2,138 (28%) agreed to undergo rapid HIV tests, and only 2 (0.09%) tested positive. Patients diagnosed with urinary tract infections, respiratory tract infections, infectious diarrhea, and pelvic inflammatory disease were more likely to be willing to undergo rapid HIV tests in the ED. Stratified analysis revealed that sexually active patients were more likely to consent to HIV testing. Therefore, non-targeted opt-in HIV testing and counseling in the ED was feasible but was not effective in a region with low HIV seroprevalence.