Many scholars, consultants and practitioners have recently focused their attention on ownership as a psychological phenomenon. It is theorised that formal ownership can produce positive attitudinal and behavioural effects through psychologically experienced ownership, and that the psychological sense of ownership may form an integral part of the individual’s relationship with the organisation. It is suggested that the presence of psychological ownership among organisational members can have a positive effect on organisational effectiveness and promote staff retention. Psychological ownership is defined as a state in which individuals feel as though the target of ownership or a piece of it is “theirs” (i.e. “It is mine!”). The main aim of the study was to explore psychological ownership from a theoretical and content validity perspective in order to develop a multi-dimensional measure of psychological ownership for South African organisations. The measure could be utilised as both a measurement and diagnostic tool to determine psychological ownership. The research methodology followed an extensive literature review of scholarly articles. A multi-dimensional framework for psychological ownership was developed, consisting of promotion-orientated and prevention-orientated psychological ownership dimensions. Promotion-orientated psychological ownership consists of six theory-driven components: self-efficacy, self-identity, sense of belonging, accountability, autonomy and responsibility. Territoriality was identified as a preventative form of psychological ownership. A panel of nine scholarly experts evaluated the validity of items and the entire theory-based instrument. Lawshe’s (1975) quantitative approach to content validity was applied in this study. The instrument was administered to a non-probability convenience sample N = 712). The sample comprised employed professional, highly skilled and skilled individuals in various South African organisations operating in both the private and public sector. The sample was randomly split into two subsets. A sample of n = 356 was used for the development of a model and the remaining half was used for validating the results that were attained from the first half. Exploratory factor analysis was performed on the one subset n = 356). Parallel analysis signified four significant factors. The study resulted in a four-factor measure comprising 35 items that was named the South African Psychological Ownership Questionnaire (SAPOS). The four factors of the SAPOS were labelled Identification, Responsibility, Autonomy and Territoriality respectively. Results of the second-order factor analysis confirmed the existence of two distinctive dimensions: promotion-orientated and prevention-orientated psychological ownership. Promotion-orientated psychological ownership comprises three components: Identification, Responsibility and Autonomy. Territoriality was identified as a dimension of preventative psychological ownership. Examination of internal consistency revealed highly satisfactory Cronbach alpha coefficients for all four factors (Identification: _= .939; Responsibility: _= .871; Autonomy: _= .874; Territoriality: _= .776). Confirmatory factor analysis on the second subset of the sample (n = 356) confirmed the four-factor model. The chi-square/df ratio (1.7), CFI (.904), RMSEA (.045), and SRMR (0.59) values met the minimum recommended standards, indicating a reasonable fit. According to the results, all items demonstrated adequate convergent validity. Examination of the variance-extracted estimates confirmed discriminant validity within the model. Evidence of criterion-related validity was provided. Promotive psychological ownership was positively related to affective commitment and job satisfaction and negatively related to turnover intentions. Independent sample t-tests and the analysis of variance technique indicated that differences exist between employees varying in biographical variables with regard to the specific dimensions (Identification, Responsibility, Autonomy and Territoriality) underlying the concept of psychological ownership. The theoretical relevance of this study is its expansion of the five-dimensional theorydriven measure of psychological ownership developed by Avey and colleagues (2009). This study expanded on their theoretical model by adding two additional promotionfocused dimensions, namely Autonomy and Responsibility. The existence of a new measure will further contribute to the body of knowledge by filling the void for such a measuring instrument for South African organisations. The methodological relevance of this study is the contribution of a multidimensional scale evidencing substantial reliability and validity for evaluating people’s psychological ownership toward their organisation. The practical relevance of this study is the contribution of a multi-dimensional measure of psychological ownership that can be utilised by Human Resource professionals and managers for clarifying psychological ownership of employees within the specific context of a multi-cultural society such as that in South Africa. Understanding and utilising the measure has the potential to increase staff retention and productivity. If a sense of psychological ownership can be created among employees by addressing the factors measured by the instrument, an enhanced workplace can be established, ensuring sustainable performance during uncertain economic times.