PURPOSE OF REVIEW: Sarcopenia and frailty are common conditions, associated with worse clinical outcomes during critical illness. Recent studies on sarcopenia and frailty in ICU patients are presented in this review, aiming to identify accurate diagnostic tools, investigate the effects on clinical and functional outcomes, and propose possible effective interventions. RECENT FINDINGS: The recent change of the sarcopenia definition underlines the importance of muscle strength over mass, this is however challenging to assess in ICU patients. There is currently no unified sarcopenia definition, nor standard frailty assessment tool; Clinical Frailty Scale is most frequently used in the ICU. Meta-analyses show worse clinical and functional outcomes for frail as well as sarcopenic patients admitted to the ICU, regardless of admission diagnosis. Frailty is a dynamic condition, worsening in severity by the time of hospital discharge, but showing improvement by 6 months post-ICU. Therapeutic interventions for frailty and sarcopenia remain limited. Although mobilization strategies show promise in improving functional and cognitive outcomes, inconsistent outcomes are reported. Heterogeneity in definitions, patient populations, and care practices challenge interpretation and comparison of study results and recognition of beneficial interventions. This highlights the need for more research. SUMMARY: The importance of preexisting sarcopenia and frailty is recognized in ICU patients and associated with worse clinical outcomes. Multidimensional interventions are most promising, including patient-tailored mobilization and nutrition.