This chapter visits the concept of social capital and provides a comprehensive review of the social capital or ‘knowing whom’ approach to careers. That approach suggests that relationship ties in the workplace and the society provide resources, such as information, influence and solidarity, that enhance individual career prospects over and above other forms of capital, including human capital. For example, both mentoring relationships and network resources, which signify social capital, relate to career outcomes. Next, the chapter focuses on how social capital is created, including behavioral tactics and other forms of capital (financial and human), while it also discusses the impact of ascriptive characteristics (e.g., gender, race) on its accummulation. This chapter continues by taking a cautionary stance with arguments and emerging empirical evidence that social capital may advance career interests of particular individuals or groups, but at the expense of the interests of the collective. This work concludes with the idea that though it may be sustainable under certain conditions to base individual career progression on the utilization of social capital, a whole system where social capital represents the major career-enhancing resource is unsustainable in the long term.