Background: It is essential for practicing dentists to have adequate knowledge of HIV/AIDS and its implications in the dental practice. Their attitudes should also be up to the professional expectations. This study aimed to assess knowledge of HIV/AIDS infection and attitudes towards its patients among dental students in Saudi Arabia. Methods: A questionnaire was prepared and distributed among a sample of dental students in Saudi Arabia. Twenty questions related to knowledge, attitudes, and oral manifestation of HIV were presented. Results: A total of 405 questionnaires were completed (67% response rate). Participants showed low knowledge of safety regarding HIV (39.5%) and 44.2% indicated that they would take an HIV test after needle stick injury. The proportion of correct answers regarding transmission of HIV through saliva, cardiopulmonary resuscitation, and aerosols by hand pieces was 41%, 37.5%, and 26.4%, respectively. Almost 50% of the surveyed dental students expressed unwillingness to treat HIV-positive patients. Poor knowledge was noted regarding oral manifestations of HIV (32.7%). Of the participants, 57.8% indicated that infection control procedures are very important for the treatment of HIV patients and 50.6% believed that a dentist can make a decision to reject the treatment of HIV patients. According to the participating dental students, the three major oral manifestations in HIV patients are hairy leukoplakia (47.4%), oral candidiasis (44.7%), and Kaposi's sarcoma (43.5%). Conclusion: Inadequate knowledge and unprofessional attitude towards HIV/AIDS patients were identified among this group of dental students in Saudi Arabia. Dental educators and health care planners in Saudi Arabia should plan to promote the knowledge and attitudes of dental students in Saudi Arabia towards the treatment of HIV patients.