Infectious complications represent one of the most common causes of morbidity and mortality in allogeneic hematopoietic cell transplant (HCT) recipients. Prophylactic and preemptive treatment strategies against bacterial, fungal, viral, and parasitic pathogens are routinely implemented during high-risk post-HCT periods at most transplant centers. The basic concepts and review of current guidelines of antibiotic prophylaxis and empirical/preemptive antibiotic treatment in allogeneic HCT recipients are reviewed in this article.