Acute chest syndrome (ACS) is a major complication of sickle-cell disease. Bacterial infection is one cause of ACS, so current guidelines recommend the routine use of antibiotics. We performed a prospective before–after study in medical wards and an intensive-care unit (ICU). During the control phase, clinicians were blinded to procalcitonin concentration results. We built an algorithm using the obtained measurements to hasten antibiotic cessation after three days of treatment if bacterial infection was not documented, and procalcitonin concentrations were all <0.5 μg/L. During the intervention period, the procalcitonin algorithm was suggested to physicians as a guide for antibiotic therapy. The primary endpoint was the number of days alive without antibiotics at Day 21. One-hundred patients were analyzed (103 ACS episodes, 60 in intervention phase). Possible or proven lung infection was diagnosed during 13% of all ACS episodes. The number of days alive without antibiotics at Day 21 was higher during the intervention phase: 15 14–18 vs. 13 13,14 days (p = 0.001). More patients had a short (≤3 days) antibiotic course during intervention phase: 31% vs 9% (p = 0.01). There was neither infection relapse nor pulmonary superinfection in the entire cohort. A procalcitonin-guided strategy to prescribe antibiotics in patients with ACS may reduce antibiotic exposure with no apparent adverse outcomes.