In Ethiopia human immunodeficiency virus (HIV) infection is a major health and socioeconomic problem. Sex workers, youth, and mobile populations all show increasing prevalence of HIV. However, there is currently no information about the seroprevalence of HIV and the knowledge of HIV among street dwellers in the country. To fill this gap, 404 street dwellers residing in Gondar, northwest Ethiopia, were included in this cross-sectional study. Socio-demographic data, factors that prompted the subjects to become street dwellers, and their knowledge about HIV were all assessed using a structured questionnaire. Stool samples for diagnosis of intestinal parasites and venous blood for HIV antibody testing were collected and processed following standard procedures. Poverty-associated movement to urban areas in search of work was reported as a major factor that forced them to live in the streets, followed by divorce, family death, and addiction and peer pressure. One or more intestinal parasites were found in 67.6% of the street dwellers. Multiple parasitic infections were detected in 27.7%. The prevalence of HIV in the street dwellers was 6.9%. Fifty-nine (16.6%) participants responded that HIV can be transmitted by eating food together. Seventy-three (18%) believed an infected needle cannot transmit HIV, while 51 (12.6%) said HIV can be transmitted by hand shaking. One hundred ninety-two (47.5%) responded that antiretroviral therapy will not prolong the life of HIV-infected individuals. In summary, the prevalence of HIV and intestinal parasitic infection was quite high among street dwellers in Gondar. Therefore, strategies to control HIV and other infectious diseases should include this group, and regular mass deworming may help to reduce the burden of infection.