Background <p>Remimazolam is a new type of ultra-short-acting benzodiazepine. The aim of this study was to investigate the effects of remimazolam, propofol and sevoflurane anesthesia on rocuronium-induced neuromuscular block.</p> Methods <p>Ninety-nine consenting patients were randomly assigned to a remimazolam group (R-group), sevoflurane group (S-group), or propofol group (P-group). Train-of-four (TOF) responses evoked on the abductor digiti minimi muscle to ulnar nerve stimulation following bolus administration of 0.9-mg/kg rocuronium were monitored with electromyography-based neuromuscular monitor. The primary outcomes were times from administration of rocuronium to first reappearance of post-tetanic count (PTC). Free plasma concentrations of rocuronium were concurrently measured at these events.</p> Results <p>Ninety patients were analyzed. No significant differences were seen in time to first PTC among the three groups. Mean (± standard deviation) and median (inter-quartile range) times for the reappearance of TOF counts 1 and 2 were significantly prolonged in S-group [50.7 ± 13.9&#xa0;min, <i>P</i> = 0.043 and 61.6 (54.3–78.0) min, <i>P</i> = 0.020, respectively], when compared with P-group [42.6 ± 10.3&#xa0;min and 52.9 (45.4–58.8) min, respectively]. However, no significant differences were seen between S-group and R-group. Median (inter-quartile range) free plasma concentration of rocuronium measured at first PTC was significantly lower in R-group [1255&#xa0;(1126–1717) ng/mL] than in P-group [1717 (1592–1961) ng/mL, <i>P</i> = 0.031].</p> Conclusions <p>These results suggest that the potentiating effects of remimazolam on rocuronium-induced neuromuscular block are weaker than those of sevoflurane and similar to those of propofol.</p>