Background : Activities of Daily Living (ADL) refer to the essential self-care tasks necessary for independent living. A 2021 study conducted in France by researchers Axelle Kostenobel and Wierle Knoop found that the loss of independent functioning is a syndrome of physiological decline, with 60% of post-surgical patients experiencing a reduction in their independence. In Mongolia, there is limited research on the ability of post-surgical patients to perform daily activities independently. Therefore, this study was conducted to address this gap. Aim: The objective of this study is to assess the level of independence among patients admitted to the Surgical Department of the Mongolian-Japanese Hospital and to analyze the interrelationships between different functional abilities. Materials and Methods: This study was conducted as a cross-sectional quantitative study involving 185 patients who underwent surgery at the Surgical Department of the Mongolian-Japanese Hospital, affiliated with the Mongolian National University of Medical Sciences. The patients’ independence levels were evaluated postoperatively using the standard six-question ADL assessment questionnaire developed by Katz et al. (1963). The collected data were analyzed using SPSS 25.0, with normality distributions assessed. Since the data did not follow a normal distribution, Spearman’s rank-order correlation coefficient was used to determine the strength of associations between variables. Results: Among the study participants, 50.8% (n=94) were male, and 49.2% (n=91) were female. The average age was 47.9±14.56 years, and the mean hospital stay was 2.7±1.6 days. The assessment of independence levels revealed that: • 11.9% (n=22) were completely dependent, • 21.1% (n=39) had impaired independence, and • 67% (n=124) maintained normal or good independence. The mean hospital stay for patients with normal or good independence was 2.51±1.42 days, while it was 2.79±1.73 days for those with impaired independence and 3.6±2.03 days for fully dependent patients. There was a weak positive correlation between independence level and length of hospital stay (r=0.159, p=0.03). Strong direct correlations were observed between: • Eating ability and dressing ability (r=0.671, p=0.001), bathing ability (r=0.568, p=0.001), mobility (r=0.571, p=0.001), toileting ability (r=0.588, p=0.001), and continence control (r=0.609, p=0.001). • Dressing ability and bathing ability (r=0.766, p=0.001), mobility (r=0.723, p=0.001), toileting ability (r=0.788, p=0.001), and continence control (r=0.736, p=0.001). • Bathing ability and mobility (r=0.789, p=0.001), toileting ability (r=0.715, p=0.001), and continence control (r=0.644, p=0.001). • Mobility and toileting ability (r=0.822, p=0.001) and continence control (r=0.770, p=0.001). • Toileting ability and continence control (r=0.909, p=0.001). Conclusion One-third of the patients admitted to the surgical department experienced a decline in independence or complete dependence postoperatively, which was weakly correlated with a longer hospital stay. The various functional abilities that determine independence were strongly interrelated.