Background <p>Total hip arthroplasty (THA) is increasing in low- and middle-income countries (LMICs) due to rising rates of hip fractures and an aging population. Identifying frail patients at risk for postoperative complications is vital for improving outcomes. This study examines the utility of the Modified 5-Item Frailty Index (mFI-5) in predicting 30-day morbidity and mortality in THA patients in resource-limited settings, where other models like the Elixhauser Comorbidity Measure (ECM) and Charlson Comorbidity Index (CCI) may be impractical due to data constraints.</p> Methods <p>This retrospective cohort study included 498 patients undergoing THA at tertiary-care hospital between January 2014 and December 2019. Patients were stratified based on their mFI-5 scores (≤ 1 vs. &gt; 1). Postoperative complications, length of stay, and mortality were compared between groups. Multivariable logistic regression was used to assess outcomes.</p> Results <p>Of the 498 patients, 62.8% had an mFI-5 score ≤ 1, and 37.2% had a score &gt; 1. Complication rates were higher in the mFI-5 &gt; 1 group (17.8%) versus the ≤ 1 group (9.6%). After adjusting for covariates, patients with mFI-5 &gt; 1 had a 97% higher likelihood of complications (aOR = 1.97, 95% CI 1.06–3.70). Each additional hospital day increased complication risk by 13% (aOR = 1.13, 95% CI: 1.05–1.21).</p> Conclusion <p>The mFI-5 is a practical, efficient tool for predicting postoperative complications in THA patients, particularly in resource-limited environments. Its use in LMICs could improve preoperative planning, reduce complications, and provide better outcome estimates for patients and healthcare providers. Given the growing geriatric population, integrating the mFI-5 into routine THA planning could enhance patient care and resource allocation. Further research is needed to validate its use across larger datasets.</p>