Objectives: We sought to determine the prevalence of traditional and complementary medicine (TCM) use for knee osteoarthritis and its associated factors among patients attending a referral hospital in an eastern coastal state of Malaysia. Methods: This cross-sectional study included 214 patients with knee osteoarthritis. A universal sampling method was applied to patients who attended the outpatient clinic in Hospital Universiti Sains Malaysia from May 2013 to October 2013. Participants were given a questionnaire to determine their sociodemographic information and a validated Bahasa Malaysia version of the Western Ontario and McMaster Universities Arthritis Index (WOMAC). This questionnaire was used to assess the severity of knee osteoarthritis (i.e., pain, stiffness, and disturbances in daily activity). Results: Over half (57.9%) of patients reported using TCM to treat knee osteoarthritis. Factors associated with TCM use were gender (odd ratio (OR) = 2.47; 95% confidence interval (CI): 1.28–4.77), duration of knee osteoarthritis (OR = 1.51; 95% CI: 1.03–2.23), and the severity of knee pain (OR = 2.56; 95% CI: 1.71–3.86). Conclusions: The prevalence of TCM use among eastern Malaysian patients with knee osteoarthritis was high. Physicians caring for these patients should be aware of these findings so that inquiries regarding TCM use can be made and patients can be appropriately counseled.