Background and Aim. Cancer is the leading cause of death in economically developed countries and is a threat to human lives. Cancer and chemotherapy side effects may affect the daily activity of cancer patients and their families on many levels confronted by changes in health status and lifestyles, leading to impaired self-care efficacy. Objective. To assess the needs and self-care efficacy for cancer patients suffering from side effects of chemotherapy. A descriptive cross-sectional design was conducted. A purposive sample of 150 adult cancer patients undergoing chemotherapy during the period from January to June 2020 was studied at the Oncology Outpatients Clinic at Al Rantisi Hospital in Gaza Strip. Tools. Tools of the study involved the following: structure interviewing questionnaire, patient assessment needs’ tool, and self-care activity for side effects of chemotherapy; Part I: assessment of self-care efficacy and Part II: assessment of physical, psychological, social, and spiritual needs of patients and activity of daily living. The findings of this study indicated that, concerning the duration of illness, 44.5% of studied patients started complaining of symptoms of cancer for about two years, and more than one-third of them, 69.3%, started chemotherapy more than one year ago. More than half of the studied patients, 55.3%, had poor knowledge about cancer, side effects of chemotherapy, how to manage these side effects, and level of self-care efficacy. The majority of studied subjects, 87.3%, had a financial burden, and nearly two-thirds of patients, 61.3%, need reassurance to cope with illness. There was high statistical significance between self-care efficacy and daily living activity. Regarding physical problem, the most affected systems were the gastrointestinal and the dermatological system. Also, the majority of patients were independent in walking, dressing, toileting, and feeding, but more than two-thirds of them needed assistance toward the ability to handle finance, shopping, housekeeping, food preparation, and travelling.