PURPOSEThe aim of this study was to examine the validity of Turkish version of Social Frailty Index in older adults.MATERIAL AND METHODS102 older adults aged 65 and over were included in the study. Hodkinson Mental Test was first applied to older adults. Older adults who scored 6 points or above were included. To evaluate the validity of "Social Frailty Index", Social Inclusion Scale, Older People's Quality of Life-Brief (OPQOL-Brief) and Lubben Social Network Scale were applied to the participants. To determine the reliability of "Social Frailty Index", the test was re-tested at one-week intervals on older adults who did not receive any treatment. Confirmatory factor analysis AMOS 23.0 was used to determine the conformity of the structure to the original model. For concurrent validity, the correlation analysis applied. Intraclass correlation coefficient (ICC [2,1], absolute agreement, 2-way random effects model) was used to determine the reliability of the scale.RESULTSThe fit of the Turkish version of Social Frailty Index to the model described in the original article was determined to be acceptable-excellent (Demographics (DEM), General Resources and Life History (GRLH), Social Activities (SA) and Fulfillment of Basic Social Needs (FBSN)) (CMIN/DF=1.36, GFI=0.93, IFI=0.90, RMSEA=0.06 and SRMR=0.07). In the correlation analysis conducted to determine its concurrent validity, Social Frailty Index had a moderate correlation with Social Inclusion Scale (r: -0.47; p<0.001) and OPQOL-Brief (r: -0.47; p<0.001). Social Frailty Index had no correlation with Lubben Social Network Scale (r: -0.03; p: 0.81). Test-retest reliability of Social Frailty Index was excellent [ICC(2,1)=0.90, %95 CI 0.84-0.93, p<0.001].CONCLUSIONThe Turkish version of the Social Frailty Index is valid and can be used to predict mortality risk based on the estimated social risk. The adapted Social Frailty Index is not adequately capturing aspects related to the network and social support.CLINICAL TRIALS NUMBERNCT06288789.