Background: Older patients visiting the emergency department (ED) are at increased risk of adverse outcomes, including ED revisits and mortality. Sarcopenia quantification by point-of-care ultrasound (POCUS) may be a useful bedside screening tool, especially when traditional frailty screening instruments, reliant on history taking, cannot be used. This study evaluated whether POCUS measurement of rectus femoris cross-sectional area (RFcsa) can predict adverse outcomes in older patients visiting the ED. Methods: In this single-centre prospective study, patients aged ≥70 years presenting to the ED of a Dutch university hospital and enrolled in the Acutelines data and biobank were included. RFcsa was measured using POCUS. ROC-analysis assessed the overall accuracy of RFcsa for prediction of the primary outcome, which was defined as the composite of ED revisit or death within 3 months. Logistic regression determined the added value of RFcsa to Karnofsky Performance Score (KPS). Results: During the study period, a total of 68 patients were included. Twenty-six patients (38%) met the primary endpoint. RFcsa showed excellent intra-rater reliability (interclass correlation coefficient=0.98). However, the accuracy to predict the composite endpoint was low, with an area under the curves of 0.53 (0.39–0.66) for unadjusted RFcsa and 0.51 (0.36–0.66) for sex-adjusted RFcsa. The addition of RFcsa in a multivariate logistic regression model with KPS did not increase the overall explained variance in the primary endpoint. Conclusion In older patients presenting in the ED, POCUS-measured RFcsa does not predict ED revisits or death within 3 months. (Trial Registration No. NCT05369962 at ClinicalTrials.gov)