Objectives: A high percentage of professional drivers (PDs) often report feeling fatigue during their work, and falling asleep at the wheel (FAW) is a major contributing factor to the occurrence of near-miss or actual accidents. The aim of this study is to evaluate the prevalence of FAW among Italian PDs and the effect of fatigue on this occurrence (corrected for the main predictive factors already known). Material and Methods: We performed a cross-sectional questionnaire survey. Data from PDs (N = 497) were used for analyses. Logistic regression analyses were performed to assess the association of reported sudden-onset sleep at the wheel with working conditions and general lifestyle factors. Results: Forty-one percent of the interviewees experienced at least 1 episode per month of sudden-onset sleep at the wheel (4.7% per week). Predictive factors of self-reported FAW were: age > 55 years old (odds ratio (OR) = 4.91, confidence interval (CI): 1.79–13.50, p < 0.01), traveling more than 40 thousand miles per year (OR = 1.86, 95% CI: 1.08–3.22, p < 0.05), body mass index ≥ 30 (OR = 2.16, 95% CI: 1.01–4.64, p < 0.05) and Chalder Fatigue Questionnaire score > 22 (OR = 3.93, 95% CI: 1.90–8.14, p < 0.01). Conclusions: There are different work and human factors underlying FAW among PDs. The Chalder Fatigue Questionnaire might be useful in measuring fatigue in this group and in detecting PDs at high risk of experiencing FAW.