Central nervous system (CNS) relapses are an uncommon yet devastating complication of non-Hodgkin lymphomas. The identification of patients at high risk of secondary CNS relapse is therefore paramount. Retrospective data indicate prophylactic CNS-directed therapies may reduce the risk of CNS involvement; however, no consensus exists about dose, timing, or route of therapy. In addition, prophylaxis is not without risk of treatment-related complications and morbidity. Here, we present a series of case vignettes highlighting our approach to common dilemmas encountered in routine clinical practice. We review the method of assessing CNS relapse risk, factors that increase the likelihood of relapse including histologic subtype, MYC rearrangement, protein expression, and extranodal involvement, and review our clinical practice based on available evidence in administering CNS-directed prophylaxis.