Introduction Dysphagia is common among survivors of critical illness who required mechanical ventilation during treatment. The risk factors associated with the development of postextubation dysphagia, and the effects of dysphagia on patient outcomes, have been relatively unexplored. Methods We conducted a retrospective, observational cohort study from 2008 to 2010 of all patients over 17 years of age admitted to a university hospital ICU who required mechanical ventilation and subsequently received a bedside swallow evaluation (BSE) by a speech pathologist. Results A BSE was performed after mechanical ventilation in 25% (630 of 2,484) of all patients. After we excluded patients with stroke and/or neuromuscular disease, our study sample size was 446 patients. We found that dysphagia was present in 84% of patients (n = 374) and classified dysphagia as absent, mild, moderate or severe in 16% (n = 72), 44% (n = 195), 23% (n = 103) and 17% (n = 76), respectively. In univariate analyses, we found that statistically significant risk factors for severe dysphagia included long duration of mechanical ventilation and reintubation. In multivariate analysis, after adjusting for age, gender and severity of illness, we found that mechanical ventilation for more than seven days remained independently associated with moderate or severe dysphagia (adjusted odds ratio (AOR) = 2.84 [interquartile range (IQR) = 1.78 to 4.56]; P < 0.01). The presence of severe postextubation dysphagia was significantly associated with poor patient outcomes, including pneumonia, reintubation, in-hospital mortality, hospital length of stay, discharge status and surgical placement of feeding tubes. In multivariate analysis, we found that the presence of moderate or severe dysphagia was independently associated with the composite outcome of pneumonia, reintubation and death (AOR = 3.31 [IQR = 1.89 to 5.90]; P < 0.01). Conclusions In a large cohort of critically ill patients, long duration of mechanical ventilation was independently associated with postextubation dysphagia, and the development of postextubation dysphagia was independently associated with poor patient outcomes.