Beside many risk factors in patients considered for alloHCT, only body mass index (BMI) as a broad marker of nutritional status has prognostic value in these patients. This is the first prospective study to investigate the validity of further nutritional markers: adjusted BMI, normalized for gender and age; Subjective Global Assessment questionnaire and standardized phase angle, normalized for gender, age and BMI in 105 patients as independent risk factors for outcomes [overall survival (OS), non-relapse mortality (NRM), relapse mortality (RM), progression-free survival (PFS)] until 2 years after alloHCT. In Cox proportional-hazards regression models, we included a variety of accepted risk factors. The two most influential pre-transplant risk factors identified and associated with similarly increased hazard ratios (HR) for OS, RM, and PFS were a low-standardized phase angle (HR = 1.97, P = 0.043; HR = 3.18, P = 0.017, and HR = 1.91, P = 0.039) and advanced disease. Under- and overweight according BMI percentiles (≤10th; ≥90th) revealed associations with increased risk of NRM (HR = 2.90, P = 0.018; HR = 3.02, P = 0.062), although only low BMI was weakly associated with OS (HR = 1.82, P = 0.09). In conclusion, our results demonstrate that pre-transplant phase angle is an independent predictor for 2-year outcomes in these patients. Further investigation is necessary to demonstrate whether the theoretically modifiable phase angle can be increased by physical training combined with nutritional support, and if this improves outcome after alloHCT.