This chapter focuses on conceptualising mentoring and other developmental relationships from a relational perspective. Relationships at work are important sources of information, learning, development and can assist with career decision making. Research on mentoring has generated substantial evidence of the outcomes of mentoring. However, there is still a lot left to be learned about how highly effective, meaningful developmental relationships function and how they are constructed and perceived as valuable by the relationship members. Our understanding of these relationships can be enhanced through examining the qualities and characteristics through a relational theory construct. We discuss various roles and functions of developmental relationships vis-à-vis relational or social cognition theory, social support theory, social capital theory, attachment theory, relatedness theory, self-in-relation theory, and leader–member exchange theory. These theories highlight various relationship characteristics with implications for relationship quality such as trust; compatibility; authenticity; dialogue, reflection and feedback; and relationship proximity. This helps explain how supportive relationships flourish and contribute to personal learning and career development. [ABSTRACT FROM AUTHOR]