Oral cancer is a life-threatening disease with low survival rates, especially when diagnosed in an advanced stage. Lack of awareness about this cancer among the population is proposed as a possible reason for this diagnostic delay. The aim of this study was to evaluate oral cancer awareness, as well as the association of this with sociodemographic status in Tehran. In this cross-sectional population-based survey, 1800 self-administered questionnaires (collecting sociodemographic data, questions regarding oral cancer awareness and the source of information) were distributed through multistage stratified random sampling. Scores for questions ranged from 0 to 4, and totals were summed. The outcome of question responses was also analyzed separately. In total, 1312 questionnaires were available for analysis, from 788 females and 489 males (37.8 ± 9.02 years). Only 30% of the respondents were aware of oral cancer. The average score for awareness was 1.09 ± 1.6 with no significant differences between age groups and genders. Almost 6.5% of participants had complete awareness about oral cancer. A significant difference was found between mean scores in different levels of education and occupation (p = 0.0001). From 585 responses to the “source of information” question, “public media” was the most important source (almost 50%). Only 2% mentioned “dentists” as a source of information. This study indicated an alarming lack of oral cancer awareness and literacy in Tehran, Iran. Dentists should be obliged to practice their pivotal role in informing the public about oral cancer.