The objective of this study was to assess tobacco use, secondhand smoke exposure, knowledge of health risks, and smoking predictors among dental students attending King Abdulaziz University, Jeddah, Saudi Arabia. A cross-sectional study was conducted and 420 dental students were invited to participate. Binary logistic regression analyses assessed the predictors of smoking. A total of 336 dental students completed the questionnaires with 25% reporting current or previous tobacco use and 96% reporting secondhand smoke exposure. Nearly half of all smokers initiated smoking during the dental program. The logistic regression results revealed that being a male (OR = 7.1, p < .0001; 95%CI = 3.7-13.4) and having a smoker in the family (OR = 2.6, p = .005; 95%CI = 1.3-5.0) increased the likelihood of smoking. In contrast, knowledge of health risks decreased the likelihood of smoking (OR = 0.90, p = .014; 95%CI = 0.82-0.98). Despite possessing knowledge about the health risks of smoking, high numbers of dental students continue to smoke and were exposed to secondhand smoke. Sex and family influence were the main pro-smoking risk factors, whereas increased knowledge of health risks was a protective factor. Tobacco control programs to reduce and/or prevent tobacco use among future dentists are needed.