Patients on maintenance hemodialysis show lower serological response to mRNA vaccines. Main causes that contribute to this phenomenon are uremic milieu and older age. However, there are no data on the impact of body composition parameters to humoral response. In this retrospective study, we used data from adult patients on maintenance hemodialysis who received vaccination with 2 doses of BNT162b2. Quantitative determination of antibodies to SARS-CoV-2 spike (S) protein receptor binding domain was performed using the Elecsys immunoassay. Antibody levels higher than 0.8 and 264 U/mL were considered positive and protective, respectively. Body composition parameters were assessed using multifrequency bioelectrical impedance spectroscopy. Overall, 49 patients were included in the study. Three weeks after the 1 vaccination, 34% of patients, and 3 weeks and 3 months after the 2 vaccination, 100% of patients had detectable titers. Protective titer was developed in 43% of patients 3 weeks after the 2 vaccination and then decreased to 24% 3 months after the 2 vaccination. More years on dialysis were correlated to the absence of protective titers. Higher prediction marker values correlated to poor antibody response, and phase angle was negatively associated with the development of protective titers. Patients with protective titers at 3 months after the 2 vaccination had significantly lower prediction marker and higher phase angle values. Parameters of body composition correlate and affect antibody response in patients on hemodialysis. The main observation is that immunogenicity of mRNA vaccines is influenced by phase angle and prediction marker.