Abstract Purpose The aim of the study was to examine patient-reported symptoms and self-care strategies in Thai patients with cancer. Methods The study was descriptive using a cross-sectional design. It was carried out at the National Cancer Institute, Thailand (Bangkok; Lopburi). 202 patients undergoing combined radiotherapy and chemotherapy (RT-CT), n = 52; or CT alone, n = 103; or RT alone, n = 47 participated. Data was collected with the use of a 25-item Therapy-Related Symptom Checklist, TRSC (Thai); a Self-Care Method scale; the Karnofsky Scale, and a Health Data form. Results Patients on combined RT-CT reported more symptoms on the TRSC, with greater severity than those receiving RT or CT alone ( F = 7.2; p < 0.01); and lower Karnofsky score ( F = 4.2, p < 0.05); Karnofsky and TRSC scores were inversely correlated. Using complementary care categories, self-care methods reported were six types: (a) Diet/nutrition/life-style changes (e.g. modify food) to manage Eating and Fatigue symptoms; (b) Mind/Body Control to relieve Fatigue and other symptoms; (c) Biologic treatment (e.g. vitamins) for eating difficulties; (d) Herbal treatments for hair loss; (e) Other methods, and (f) taking prescribed medicines to control pain and other symptoms. Some patients reported “doing nothing” as coping. Conclusions Self-care including complementary care use as an adjunct to cancer treatments could help patients deal with the side effects of therapy. Assessment of symptoms using the TRSC (Thai) version and their alleviation could enable the health care providers to enhance patients' coping during cancer treatments.