Background: Sleep deprivation is considered a stress factor in the perioperative period. There are several studies on sleep disturbance after surgery but very limited literature available on preoperative sleep patterns, predictors of sleep disturbance and its effect on surgical outcome. Methodology: Patients scheduled for thoracic surgery were asked to fill out a written Pittsburgh Sleep Quality Index (PSQI) questionnaire. The primary investigator explained this form to all the patients. This was filled out before premedication for subjective assessment of sleeping pattern at two different time point. Only those patients included who spent the previous night at home. Participants were asked to respond to the questions regarding their baseline sleeping pattern and compare it with last night. Results: Total eighty-three patients with a mean age of 47.83 ± 17.88 were included in the study. Overall mean PSQI scores were significantly higher (p-value < 0.01) during the night before surgery (6.94 ± 2.115) when compared with baseline (3.88 ± 1.877). Sleep latency was also significantly affected when last night-1 (the night before admission) was compared with usual sleep latency. Twenty patients were unable to sleep more than 5 hrs at night before admission which was significant when compared with their last month status (20 vs 3). Logistic regression model demonstrated the age and Timing of surgery as a strong predictors of poor sleep (defined as PSQI ≥ 5). Conclusion: Quality of sleep was profoundly affected at night before thoracic surgery, mainly due to a significant change in sleep latency and sleep duration. Although age and Timing of surgery were strong predictors of poor sleep we were unable to find any association between quality of sleep and type of surgery.