Sarcopenia, defined as loss of muscle mass, can occur with aging. We conducted a single-center retrospective analysis to evaluate the impact of muscle quality in multiple myeloma (MM), a hematologic cancer of older adults, undergoing autologous hematopoietic cell transplantation (autoHCT). Healthy muscle was quantified by measuring the percent of high-density muscle within the L3 psoas muscle using a novel computed tomography method in 142 eligible patients. Early post-transplant complications were assessed in the first 100 days after transplant. Sarcopenia, defined as ≤80% high-density muscle, was found in 72 (51%) patients. Sarcopenic obesity, defined as sarcopenia and a BMI ≥ 30, was found in 32 (23%) patients. One or more early complications occurred in 22 (16%) patients. Cardiovascular events accounted for 36% of all complications. Patients with sarcopenia had more cardiac complications (12.5%) than patients without (2.9%, p = 0.03). Multivariate analysis revealed increased BMI at transplant, but not sarcopenia, was associated with worse OS (hazard ratio: 1.11, 95% confidence interval: 1.02-1.22, p = 0.02). Our analysis suggests that sarcopenia is prevalent in MM and associated with increased early post-transplant cardiovascular complications in MM. Obesity, regardless of sarcopenia, is associated with worse survival in MM. Our study generates hypothesis-generating data to risk-stratify patients being considered for autoHCT.