Multivitamins (MVi) are broadly used by cancer patients to improve overall health and energy. Fatigue is a common symptom in cancer patients including those receiving radiation therapy. We conducted a trial of MVi versus placebo in patients with breast cancer (BC) undergoing radiation therapy (Rxt) to evaluate if MVi would affect fatigue and quality of life. We randomized patients at the beginning of Rxt treatment to either placebo or Centrum Silver® (Wyeth-Whitehall laboratory). At the middle of the radiation treatments patients were switched from placebo to MVi and vice versa. Patients answered to the EORTC QLQ C-30 quality of life (QOL) and Chalder Fatigue Questionnaires at the beginning, the time of switching and at the end of Rxt. We found that both groups experienced significant decreases in general and physical fatigue at the end of the course of placebo compared to the assessment prior to this treatment. We also observed significant improvements in functional and symptoms in the patients on placebo. When we compared different groups of patients we also observed significantly lower rates of physical and general fatigue in the patients who had just finished a course of placebo as compared to patients finishing course of MVi. We conclude that MVi do not improve radiation related fatigue, and may in fact have a deleterious effect on fatigue and decrease QOL in patients with BC undergoing Rxt.