A large body of literature documents the increasing adoption of fee-for-service models, competitive marketing strategies, corporate governance structures, and business rhetoric in the human service sector as well as in the nonprofit and public sectors more broadly. Authors have argued that neoliberal policies of government austerity, performance-based contracting, and consumer-side subsidization have instilled businesslike operations and competitive relations in the human service sector since the 1980s, leading to an incursion of market practices and a threat of mission drift. However, though neoliberal policy shocks have certainly driven organizational change in social welfare systems, I argue that the overwhelming focus on developments in the late twentieth century has obscured historical evidence pointing to longstanding and deep-rooted market influences in the sector. This lack of historical perspective perpetuates a myopic view of market forces as externally imposed and relatively recent. Focusing on U.S. social work history and based on extensive archival and secondary analysis, this dissertation offers a farther-reaching perspective on the interplay of self-interest and altruism in this critical institutional pillar of American society. Specifically, the dissertation examines three important cases of field-level organizational change in American social work: 1) the rise and justification of fee-charging policies; 2) the development of agency-based client outcome evaluation practices; and 3) the formation and attenuation of hierarchical fundraising and service planning networks. The dissertation comprises three self-contained articles that draw on a variety of sociological principles and perspectives, yet each article contributes to an overarching argument about the nature of managerialism and market relations in professional service domains. Proposing a conception of marketization as organizational disembedding, I highlight a persistent tension between collective professional priorities and individual organizational commitments. From this perspective, marketization can be understood partly as the process by which interest becomes centered in individual organizational actors rather than in diffuse professional communities. As modern society vests formal organizations with a growing sense of independent actorhood, it is important to understand the process and implications of disembedding, not only for the sociological study of organizations but also for the increasingly collaborative and relational forms of cross-sector governance that have taken root in the United States and other societies with large human service sectors.