(1) Background: Leclercia adecarboxylata (L. adecarboxylata) is a gram-negative bacillus of the Enterobacteriaceae family, which is uncommonly isolated from clinical specimens. L. adecarboxylata is considered as an aquatic opportunistic pathogen and most of the human infections are polymicrobial and usually occur in immunocompromised hosts. (2) Methods: In this retrospective study, we included all L. adecarboxylata strains since the introduction of MALDI-TOF MS in the Microbiology Department of Nord Franche-Comté Hospital, France (from 1 March 2015 to 31 July 2019). We studied demographic characteristics, comorbidities, characteristics of the current infection and outcome as well as antimicrobial susceptibility testing in all isolates. (3) Results: A total of 8 samples were identified (in 6 patients (4M/2F), with a recurrent L. adecarboxylata infection in 2 patients). The patients’ mean age was 66.2 years (range: 19–84). All patients were considered as immunocompetent, except a peritoneal dialysis patient with kidney transplantation. An exposition to an aquatic environment was identified in one patient. The most prevalent clinical feature was catheter-associated male urinary tract infection (in 3 cases) followed by ventilator-associated pneumonia (in 2 cases). One of 6 patients presented L. adecarboxylata bacteremia. L. adecarboxylata was part of a polymicrobial infection in 4 patients. The isolates showed a high susceptibility to all tested antibiotics, except one strain, which was resistant to fosfomycin. All patients with L. adecarboxylata infection were treated with antibiotics with a favorable outcome. (4) Conclusion: This study confirms the pathogenicity of L. adecarboxylata, even in immunocompetent patients, with a high susceptibility to antibiotics.