To evaluate the effects of the replacement of ceftriaxone by cefotaxime on the incidence of third-generation cephalosporin-resistant Enterobacterales (3GC-RE). We conducted a 24-month monocentric prospective, stepped-wedge cluster randomized controlled trial. During the control phase of the study, clinicians prescribed either ceftriaxone or cefotaxime. During the intervention phase, they systematically prescribed cefotaxime. The cefotaxime/ceftriaxone ratio was inversely correlated with the incidence of 3GC-RE. All in all, 3GC-RE incidence was 1.05 (27/25,692) acquired cases/1000 hospitalization days during the control phase and 0.54 (11/20,419) acquired cases/1000 hospitalization days during the intervention phase (incidence rate ratio IRR = 0.51 0.22-1.07, p = 0.06). In multivariable analysis, intervention phase (versus control phase) (p = 0.007), cefotaxime/ceftriaxone ratio (p = 0.003) and imported 3GC-RE (p = 0.005) were associated with the incidence of acquired cases of 3GC-RE. We found that replacing ceftriaxone with cefotaxime reduced the occurrence of 3GC-RE isolates. More studies are needed to confirm these results.