Asparaginase is a critical component of acute lymphoblastic leukemia (ALL) treatment in children; however, its use in adults is often avoided as a result of toxicities including hepatotoxicity, thrombosis, and pancreatitis which have been reported more commonly in adults than in children. In this retrospective analysis, short-acting L-asparaginase (L-ASP) and long-acting polyethylene glycol (PEG)-asparaginase (PEG-ASP) were compared for grade 3-4 toxicities and characterized by patient and drug-related factors to identify strategies for toxicity avoidance in adults with ALL. Asparaginase was administered during sequential courses of chemotherapy using a pediatric-inspired treatment regimen. Forty-eight patients who received PEG-ASP and nine patients who received L-ASP were identified. The rates of toxicity were as follows for the PEG-ASP and L-ASP groups, respectively: hepatotoxicity (60% vs. 33%, P = 0.275), pancreatitis (17% vs. 22%, P = 0.650), thrombosis (19.0% vs. 0%, P = 0.328), or any grade 3-4 toxicity (71% vs. 44%, P = 0.143). Toxicity did not correlate with dose, either by individual dose based on flat or BSA-based measures. Logistic regression identified obesity as a risk factor for heptatotoxicity (OR = 8.44, 95% CI: 1.395-51.117). Hypofibrinogenemia was identified as a pharmacodynamic marker for predicting hepatotoxicity. In conclusion, grade 3-4 toxicity was not statistically different between adult ALL patients receiving PEG-ASP and L-ASP, but toxicity was strongly associated with obesity and hypofibrinogenemia, not dose.