This chapter details the role of and design of cross-sector social partnerships (CSSPs) at the local level. It highlights the emergence and diffusion of CSSPs for solving community-wide social problems, by showcasing the role of partnerships for local sustainability and the uptake of collaborative community sustainability strategies (such as Local Agenda 21s). It contrasts a partnership (collaborative) approach with a participation (consultation) approach to formulating and implementing a strategic plan. In addition, the chapter uses four case studies about collaborative community sustainability strategies to consider the advantages and disadvantages of different ways to design a CSSP. These four cases all focus on the implementation of a collaborative strategic plan, and consider structural features such as the decision- making entity, the partner engagement mechanisms, the communication systems, the monitoring systems, and the involvement of partners in action-taking. By considering the comments of 63 interviewees - representing local authorities, large corporations, business associations, non-governmental organizations, universities, and small- & medium-sized enterprises – conclusions are drawn about the perceived advantages and disadvantages of four different CSSP designs. These results show that if partnerships are to be considered as a means to engage responsible businesses in community sustainable development (or other social issues at the local level), then the design of their ongoing (implementation) structure is a critical consideration. This is particularly true for CSSPs that are aiming to achieve collaborative goals, CSSPs addressing complex topics that require a long-term partnership and/or CSSPs with a large number of organizations involved. This chapter provides insights for both practitioners and collaboration scholars. Given the choice of case studies, it is also relevant for those interested in community sustainability, sustainable development, and strategic management.