Purpose Sarcopenia, a comprehensive marker of frailty, is assessed by evaluating the combination of muscle function (MF) and muscle mass (MM). Herein, we aim to evaluate the prognostic implication of sarcopenia assessed by MF, and pre-defined MM from a routine pre-operative chest Computer Tomography (CT), in patients undergoing cardiac surgery. Methodology This study included 237 patients who underwent cardiac surgery with sternotomy and pre-operative CT Chest from 2019 to 2023 at Townsville University Hospital, Australia. Measurement of Pectoralis Major Area (PMA) dimensions from routine pre-operative CT chest was performed. This was evaluated as the average attenuation of segmented left and right muscle. The sarcopenia cut-off value was defined as the lowest sex-specific quartile in PMA with the cut-off values for PMA of 1045mm2 and 609mm2 for males and females, respectively. MF of the last 30 patients from the cohort were assessed with handgrip strength and 5-time chair rise test, as per the Revised European Working Group of Sarcopenia in Older People 2 (EWGSOP). Intra and post-operative outcomes up to 30-days, were collected. Results Among the 30 patients assessed for their MF and MM, 10 patients were identified with sarcopenia from both pre-defined MF as well as our newly define MM. Sarcopenic patients required significantly longer hospitalization (8.6±2.32 vs. 6.55±3.07 days; P=0.021). Logistic Regression Analysis confirmed that sarcopenia with the imaging cut-off values is associated with increased hospital length of stay (OR = 6.0, 95% CI: 1.13-31.99, p=0.036). There was a trend towards longer ICU stays and increased post-operative complications in sarcopenic patients. Conclusion In this pilot study, sarcopenia based on pre-operative CT Chest measurement of pectoralis muscle dimensions and EWGSOP defined muscle function may predict hospital length of stay after cardiac surgery. Further evaluation of sarcopenia with this simple measurement is warranted in larger cohort studies.