Food-drug interphase products, referring to nutraceuticals in this study, are a category of health products containing a combination of food ingredients with active substances for oral consumption. Many of these products are marketed as an alternative to prescription medicine to treat various ailments despite the lack of scientific evidence, influencing patients with chronic diseases to consume nutraceutical products. This study aimed to determine the prevalence and factors associated with knowledge, attitude, and practice of nutraceutical use among patients with chronic disease attending to the outpatient clinic. This is a cross-sectional study involving patients with chronic disease at the outpatient specialist clinic. Samples were recruited from the outpatient clinic using convenience sampling. Data was collected using a self-administered questionnaire, which was self-constructed and validated. We found that the use of nutraceuticals was prevalent among 17.9% of respondents. More than half (60.9%) of the respondents have poor knowledge of nutraceutical and 53.1% of respondents have a positive attitude towards nutraceutical. Gender and morbidities were the factors associated with the practice of nutraceutical usage. Female patients are more likely to have increased use of nutraceutical than male patients and patients with multiple morbidities have higher odds of using nutraceutical than patients with single morbidities. There is a high number of patients who consume nutraceutical products and public knowledge of nutraceutical needs to be improved further. The government should develop appropriate regulation and monitoring of nutraceutical products.