Background: Postoperative complications after esophagectomy are thought to be associated with reduced fitness. This observational study explored the associations between aerobic fitness, as determined objectively by preoperative cardiopulmonary exercise testing (CPEX), and 30-day morbidity after esophagectomy. Methods: We retrospectively identified 254 consecutive patients who underwent esophagectomy at a single academic teaching hospital between September 2011 and March 2017. Postoperative complication data were measured using the Esophageal Complications Consensus Group definitions and graded using the Clavien-Dindo classification system of severity (blinded to cardiopulmonary exercise testing values). Associations between preoperative cardiopulmonary exercise testing variables and postoperative outcomes were estimated using logistic regression. Results: A total of 206 patients (77% male) were included in the analyses, with a mean age of 67 years (SD 9). The mean values for the maximal oxygen consumed at the peak of exercise (VO 2peak) and the anaerobic threshold were 21.1 mL/kg/min (SD 4.5) and 12.4 mL/kg/min (SD 2.8), respectively. The vast majority of patients (98.5%) had malignant disease—predominantly adenocarcinoma (84.5%), for which most received neoadjuvant chemotherapy (79%) and underwent minimally invasive Ivor Lewis esophagectomy (53%). Complications at postoperative day 30 occurred in 111 patients (54%), the majority of which were cardiopulmonary (72%). No associations were found between preoperative cardiopulmonary exercise testing variables and morbidity for either VO 2peak (OR 1.00, 95% CI 0.94–1.07) or anaerobic threshold (OR 0.98, 95% CI 0.89–1.09). Conclusion: Preoperative cardiopulmonary exercise testing variables were not associated with 30-day complications after esophagectomy. The findings do not support the use of cardiopulmonary exercise testing as an isolated preoperative screening tool to predict short-term morbidity after esophagectomy. This modestly sized observational work highlights the need for larger studies examining associations between preoperative cardiopulmonary exercise testing and outcomes after esophagectomy to look for consistency in our findings.