Narcissism has recently been widely studied in the various subfields of psychology and in organizational behavior research. Narcissism is a structure that is studied under different classifications and related to this with various dimensions. In this context, it is examined at level of personality disorder or pathological narcissism in clinical research and at the subclinical level in social psychology and organizational psychology research. In addition, there are classifications of vulnerable, grandiose, normal, hypersensitive, collective narcissism. Within each classification, different aspects of narcissism are examined. Therefore, it is difficult to measure narcissism with a single item. In this study, it is aimed to obtain further findings on the psychometric properties of the Turkish version of Single Item Narcissism Scale (SINS-T) which was developed by Konrath, Meier, & Bushman (2014), and adapted into Turkish culture by Ozsoy et al. (2017). In this direction, psychometric properties of SINS-T were investigated in two separate studies (study 1 n = 349, study 2, n = 236, Total N = 585). In study 1, with Dark Triad components (i.e., narcissism, Machiavellianism, and psychopathy) on sample group of academicians; In the study 2, with five factor personality traits and NPI-16, on a heterogeneous employee group, the psychometric properties of SINS-T has been examined. With those variables the convergent and discriminant validity of SINS-T (with nomological networks and multi-method multi-method approach) were examined. In both studies, the score of SINS-T of men was higher than women. In both studies, the psychometric properties of SINS-T met the expectations of validity at a certain level. However, based on the limitations of single item scales, narcissism-specific constraints and the limitations of current research, it thought that SINS-T should not be considered as a competitor to current narcissi scales but it can be used as an alternative scale. In the discussion section, the findings of the study were interpreted and the limitations and criticisms of the study and SINS-T were emphasized. Key words: Narcissism, Single Item Narcissism Scale, Psychometric Properties, Limitations, Criticisms