Patients who undergo autologous hematopoietic stem cell transplantation (autoHSCT) often experience reduced oral intake and wasting. We examined their daily nutritional intake, assessed alterations in body composition and muscle strength, and explored associations between decreased nutritional intake and treatment outcomes. This retrospective study included 64 patients. Their food record charts and parenteral nutrition (PN) prescriptions from medical records were used to assess nutritional intake. Body composition and handgrip strength data were obtained from dietitian records. Patients consumed >75% of their nutritional requirements through an oral diet in 6.7 days, 50-75% in 4.8 days, 25-50% in 5.0 days, and <25% in 3.1 days. The average oral intake was 62% of the requirement and was partially supplemented with PN. Patients experienced a mean decrease in body weight of 2.9 ± 3.0 kg, with 2.3 ± 3.4 kg of lean mass, and a mean reduction in handgrip strength of 3.5 ± 3.6 kg. We found a positive correlation of caloric deficits with weight loss and handgrip strength reduction and negative correlation with time to neutrophil engraftment and duration of hospitalization. This study highlighted a notable reduction in oral nutritional intake following autoHSCT. While caloric deficits might affect outcomes, further investigation is warranted to explore this observation.