Background: Switzerland’s demographic trends show, as elsewhere on the planet, increasing numbers of older and very old adults. This suggests that its healthcare system will suffer serious repercussions, including in the use of care and especially the use of emergency services. Significant numbers of older adults will be at risk of developing multiple chronic conditions including one or more geriatric syndromes, such as frailty and delirium. Few studies to date have documented associations between frailty and delirium. Aim: To explore the relationships between frailty and delirium in older adult patients consulting (n = 114) at an emergency department (ED) in Switzerland. Method: A cross-sectional study was conducted in a peripheral hospital ED in the French-speaking part of Switzerland. Frailty was assessed using the Tilburg Frailty Indicator (TFI). Delirium was assessed using the Confusion Assessment Method (CAM). Participants’ cognitive states were assessed using the 6-item Cognitive Impairment Test (6CIT) and the Informant Questionnaire on Cognitive Decline in the Elderly (IQ-CODE), completed by the participant’s most significant informal caregiver. Results: The mean participant age was 77.6 years (SD = 7.7); the majority of the subjects were women (54%). The participants took an average of 4.7 different medications a day (SD = 3.2, median = 4). More than half (62%) of the participants were frail; 2 and 14% presented signs and symptoms of delirium and subsyndromal delirium, respectively. A weak but significant association between scores for frailty and delirium (p < 0.05) was demonstrated, and clinical observation confirmed this. A 4-h follow-up measurement of delirium in the ED revealed no significant or clinical difference. Conclusion: Although the literature describes strong associations between frailty and delirium in surgical units and community care settings, the present study only demonstrated a weak-to-moderate association between frailty and delirium in our ED