Background: Early detection of delirium among home-dwelling older patients is a substantial challenge for home health care providers. Despite an abundance of literature, recent studies still describe a widespread lack of knowledge about delirium and its underdetection in all types of health care settings. Aims and objectives: This study aimed to assess the knowledge of community health care nurses (CHNs) about delirium in the Switzerland's French-speaking region. Methods: A cross-sectional observational study involving 75 CHNs was conducted between February and July 2015. Data were collected using an autoadministered questionnaire based on the study by Malenfant and Voyer, exploring theoretical knowledge of delirium and its detection using clinical vignette case studies. Outcomes were analyzed using descriptive statistics. Results: Forty-eight CHNs participated in the study; nearly all of them (44; 94%) selected the correct definition of delirium, and most (36; 78%) knew its four principal diagnostic criteria. Only 16 (34%) participants selected the confusion assessment method (CAM) as the recommended best practice delirium detection tool. Only 19 (40%) and 23 (49%) participants were able to correctly identify hypoactive and hyperactive delirium, respectively, from the clinical vignette case studies. The average score of CHNs on the Malenfant and Voyer's questionnaire was 12.7 (SD 3.2). Conclusion: Participants showed moderate-to-low knowledge about delirium. The study identified a lack of knowledge on how to recognize the signs and symptoms of delirium and the absence of suitable delirium detection tools.