Background: No investigation has assessed frailty in the clinical setting of thermal/spa facilities, which often receive older patients with osteo-articular and musculoskeletal conditions. Objective: To examine the prevalence of frailty in older adults receiving thermal/spa treatment and to gather preliminary evidence about the feasibility of integrating geriatric assessments, including frailty, in the routine clinical consultations in spa facilities. Methods: Mixed design, with a quantitative cross-sectional investigation performed among 197 volunteer patients (mean age 73.2 ± 6.4 years-old; 82.2% women) of seven French thermal/spa facilities and a qualitative investigation (semi-structured interviews) with the nine physicians working in the participating facilities. Frailty was defined according to a modified Fried frailty phenotype based on six self-reported criteria (including mobility impairment, nutritional status, and fatigue): individuals meeting ≥3 criteria were considered frail; 1-2 criteria, pre-frail; no criterion, robust. Interviews with the participating physicians on the feasibility of integrating geriatric assessments in routine clinical consultations at spa facilities were recorded and their content, analyzed. Results: Frailty was detected in 112 individuals (56.9%), 26 (13.2%) were considered prefrail, and 59 (29.9%), robust. Regarding the interviews, three physicians indicated the geriatric assessments could be integrated in the routine spa consultations; two, in the consultations of specific/targeted patients, but not in routine; two, only in the context of health education; two, in the context of research protocols. The content of interviews highlighted geriatric assessments provided a better overview of the health/clinical status of the patients. Conclusion: Frailty is very prevalent in older patients of spa facilities. Such facilities may constitute an interesting clinical setting for screening for frailty through the implementation of geriatric assessments.