The aim of this study was to evaluate the effect of preoperative delay on the efficacy of video-assisted thoracoscopic surgery (VATS) for post-pneumonic pleural empyema (PPE). This was a prospective study of 39 consecutive patients with PPE who were treated by VATS with curative intent over a 4-year period. Failure to obtain full lung re-expansion resulted in conversion to thoracotomy. Pre- and post-operative variables were correlated with surgical outcome. VATS debridement was successful in 16 (41%) patients while conversion to open decortication was needed in 23 patients (21 immediate, two delayed), There was no difference in the age/sex distribution of the two groups. In the failed VATS group the delay from hospital admission to operation was longer: 24 (2.1) vs. 16.6 (2.7) days (P = 0.03, 95% CI 0.53-14.3 days); operating time was longer: 128.2 (7.9) vs. 86.2 (10.4) min (P = 0.003, 95% CI 15.2-68.5 min) and post-operative stay was longer: 8.4 (0.8) vs. 5.2 (0.6) days (P = 0.03, 95% CI 1.1-5.3 days). VATS can be used successfully to treat PPE with a faster post-operative recovery when successful than open surgery. Delayed surgical intervention decreases the success of VATS thus earlier referral for surgical intervention in PPE (ideally within 21 days) is advocated to gain its full benefits.