Background/Objectives: Sarcopenia is a growing public health challenge in older adults, being associated with functional decline, frailty, and increased mortality. The SARC-F questionnaire is a widely recommended screening tool for sarcopenia; however, no validated Croatian version has been available so far. This study aimed to translate, culturally adapt, and validate the Croatian version of the SARC-F questionnaire for older adults. Methods: In a cross-sectional design, 153 participants aged ≥ 65 years from Zagreb and Bjelovar were enrolled between March and September 2025. Psychometric evaluation included internal consistency (Cronbach’s α), test–retest reliability (intraclass correlation coefficient, ICC), item–total correlations, and split-half reliability. Convergent validity was assessed via correlations with handgrip strength (HGS), Short Physical Performance Battery (SPPB), and timed up-and-go (TUG) tests. Known groups and construct validity were also examined. Results: The Croatian SARC-F showed good internal consistency (Cronbach’s α = 0.76; 95% CI: 0.70–0.82), with item–total correlations ranging from 0.34 (falls) to 0.80 (stairs) and excellent test–retest reliability (ICC = 0.86). Strong correlations were found with SPPB (ρ = −0.50; p < 0.001), TUG (ρ = 0.50; p < 0.001), and handgrip strength (ρ = −0.42; p < 0.001), supporting convergent validity. An exploratory factor analysis indicated a unidimensional structure explaining 43% of the variance. Conclusions: The Croatian version of SARC-F is a reliable, valid, and clinically feasible tool for identifying older adults who are at risk of sarcopenia. The results support its use in national screening and cross-cultural research across Europe.

Background: Population aging represents a major public health challenge, accompanied by an increasing prevalence of chronic diseases and age-related functional decline. Declines in lower-extremity physical function are particularly important, as they are strongly associated with mobility limitations, loss of independence, increased risk of falls, hospitalization, and mortality in older adults. Reliable and valid tools to assess physical performance are therefore essential in both clinical and research settings. The Short Physical Performance Battery (SPPB) is a widely used instrument for assessing lower-extremity physical performance in older adults and is recommended within the diagnostic algorithm of the European Working Group on Sarcopenia in Older People (EWGSOP2) for evaluating physical performance severity. However, the SPPB has not yet been psychometrically validated in the Croatian older population. This study aimed to evaluate the reliability and validity of the SPPB in Croatian older adults. Methods: This study examined the metric properties of the SPPB in a sample of 153 older adults recruited from nursing homes and community settings. Results: The SPPB demonstrated acceptable internal consistency (Cronbach’s alpha = 0.74) and good test–retest reliability (ICC = 0.893) for the total score. Convergent and construct validity were supported by significant associations with established measures of functional mobility and muscle strength. Conclusions: The Croatian version of the SPPB is a reliable and valid instrument for assessing lower-extremity physical performance in older adults. Its use is supported in clinical practice and research settings in Croatia. Further studies should examine responsiveness and predictive validity in nationally representative samples.