To evaluate the effect of procalcitonin-guided management on the duration of antibiotic therapy in critically ill cancer patients with sepsis. Randomized, controlled, single-blinded trial. A comprehensive multidisciplinary cancer hospital in Jordan. Adults with cancer treated in the ICU who were started on antibiotics for suspected infection, met the SEPSIS-3 criteria, and were expected to stay in the ICU greater than or equal to 48 hours. Patients were randomized to the procalcitonin-guided or standard care (SC) arms. All patients had procalcitonin measured daily, up to 5 days or until ICU discharge or death. For the procalcitonin arm, a procalcitonin-guided algorithm was provided to guide antibiotic management, but clinicians were allowed to override the algorithm, if clinically indicated. In the SC arm, ICU clinicians were blinded to the procalcitonin levels. Primary outcome was time to antibiotic cessation. We also evaluated the number of antibiotic-free days at 28 days, hospital discharge, or death, whichever came first, and antibiotic defined daily doses (DDDs). We enrolled 77 patients in the procalcitonin arm and 76 in the SC arm. Mean age was 58 ± 14 (sd) years, 67% were males, 74% had solid tumors, and 13% were neutropenic. Median (interquartile range [IQR]) Sequential Organ Failure Assessment scores were 7 (6-10) and 7 (5-9) and procalcitonin concentrations (ng/mL) at baseline were 3.4 (0.8-16) and 3.4 (0.5-26), in the procalcitonin and SC arms, respectively. There was no difference in the median (IQR) time to antibiotic cessation in the procalcitonin and SC arms, 8 (4-11) and 8 (5-13), respectively (p = 0.463). Median (IQR) number of antibiotic-free days were 20 (17-24) and 20 (16-23), (p = 0.484) and total DDDs were 1541.4 and 2050.4 in the procalcitonin and SC arms, respectively. In critically ill cancer patients with sepsis, procalcitonin-guided management did not reduce the duration of antibiotic treatment.