This paper describes the prevalence of mood disturbance, sleep disturbance, fatigue and pain (MSFP), either alone or in combination in patients receiving cancer therapy, and determines its impact and whether it is a predictor for functional status and the impairment of quality of life (QoL). This is a cross-sectional study using secondary data from a sample of 214 patients being treated by chemotherapy or radiotherapy. In all, 87%, 68%, 66% and 38% of the patients reported MSFP respectively. Co-occurrence of any three and all of the four symptoms, were reported separately at rates of 29% and 31%. Patients with all four symptoms recorded significantly lower Karnofsky Performance Scale (KPS) scores (mean 77.7 ± 12.9) and QoL scores (mean subscales scores 9.0-17.6) than those with none or up to any three of the symptoms (P < 0.001). Regression of the KPS and QoL scores against the MSFP revealed an increase in the explained variance of 25%, 43%, 27%, 37% and 41% respectively for KPS, physical, emotional, functional and total QoL. The results suggest that MSFP are highly prevalent, whether alone or in combination, in patients receiving cancer therapy, and may negatively influence the patient's functional status and QoL during cancer therapy.