The purpose of this study was to discover and describe the structure and essential meaning of the experience of betrayal in intimate relationships. Previous and current research has directed much attention to the consequences and effects of betrayal in relationships, however the essential experience of the phenomenon of betrayal has received less attention. The experience of betrayal was approached from a Kleinian perspective. A review of the literature revealed that betrayal per se is less frequently found in psychological texts although extensive reference to the construct is found in the field of sociology, in texts on deviance (Ben-Yehuda, 2001). However, inherent aspects of the phenomenon may be recalled for the purposes of this study, notably trust and loyalty. Trust is considered to be an intrinsic variable in the phenomenon of betrayal. Loyalty appears to be an interchangeable variable and is briefly included in this study. Trust as a significant aspect in the establishment of human relationships was discussed with reference to relevant psychological paradigms. The bridge to Kleinian theory was formed using trust as a fundamental aspect of the primary mother-infant relationship. Further exploration of core Kleinian constructs and Klein’s developmental positions, were also integrated in elucidating the phenomenon of betrayal in intimate relationships. Being qualitative in nature, the experience of betrayal was explored using research principles of grounded theory (Strauss&Corbin, 1990/1998) for the purposes of data reduction, analysis and generation of theory. In addition, the qualitative research interview, proposed by Kvale (1996), was used to collect the data. In-depth interviews with five participants and a second interview with one of the participants were conducted. The participants were unknown to myself as the researcher, prior to commencing the study and they were formally approached by three fellow practising psychologists. Furthermore, the study of the experience of betrayal included verification of the transcribed interviews by the participants, prior to data reduction and analysis. In this manner, opportunities for further reflection and an enhanced understanding of the experience of betrayal were provided. The core category which emerges from this inquiry is a sense of alienation which individuals experience as a result of betrayal in intimate relationships. Therefore, contrary to Klein’s extensive emphasis on intrapsychic processes, the interpersonal nature of individuals cannot be excluded or underestimated. These findings specifically contribute to Kleinian theory, social psychology, sociology, theology and psychotherapy. In this study the participants’ experience of betrayal, the consequences for the participants themselves and the outcome of the relationships were addressed. Furthermore, the significance of cognitive processes in adulthood and the theoretical implications of the relational phenomenon of betrayal for further research were mentioned. Contributions to Klein’s theory as well as a critical review of the research methodology and a critique of the strengths and limitations of this study were also included.