Abstract Background Current guidelines and literature support the use of therapeutic drug monitoring (TDM) to optimize β-lactam treatment in adult ICU patients. Objectives To describe the current practice of β-lactam monitoring in French ICUs. Methods A nationwide cross-sectional survey was conducted from February 2021 to July 2021 utilizing an online questionnaire that was sent as an email link to ICU specialists (one questionnaire per ICU). Results Overall, 119 of 221 (53.8%) French ICUs participated. Eighty-seven (75%) respondents reported having access to β-lactam TDM, including 52 (59.8%) with on-site access. β-Lactam concentrations were available in 24–48 h and after 48 h for 36 (41.4%) and 26 (29.9%) respondents, respectively. Most respondents (n = 61; 70.1%) reported not knowing whether the β-lactam concentrations in the TDM results were expressed as unbound fractions or total concentrations. The 100% unbound fraction of the β-lactam above the MIC was the most frequent pharmacokinetic and pharmacodynamic target used (n = 62; 73.0%). Conclusions Despite the publication of international guidelines, β-lactam TDM is not optimally used in French ICUs. The two major barriers are β-lactam TDM interpretation and the required time for results.