This research contributes to academic understanding of diversity in policy-networks, emphasising three main facets of diversity: first, diversity as policy novelty, new solutions emerging from strategic actors in policy-making debates; second, diversity of beliefs and values within a coalition, an advocacy strategy to enhance an actors’ credibility; third, diversity as a proxy for legitimacy, when a debate includes issues from diverse sources, or when policy positions are represented collectively through coalitions, often polarised across diverging ideological continuums. The three papers of this thesis address these facets, presenting theoretical frameworks that benefit scholars working on the formation of coalitions, policy networks and entrepreneurs, and legitimacy in policy-making processes. The results suggest three overarching considerations in respect to diversity. First, diversity, in the form of novel policy positions, emerges strategically when actors in favourable network positions deploy entrepreneurial assets, such as financial resources and credibility. This enhances academic understanding of the extent to which endogenous and exogenous features have multiplicative effects on policy novelty. Second, credibility can be a motive for actors to join heterogeneous coalitions with diverging beliefs and values. Strategies such as greenwashing that enhance the credibility of the narrative of certain policies and actors can explain why coalitions include members with heterogeneous beliefs and values. Thus, the homogeneity of beliefs within a coalition, a core assumption in the literature, is complemented with explanations that portray diversity in coalitions as the outcome of strategic behaviour of interest groups to enhance their influence. Third, a new methodological approach allows a more sophisticated measure of diversity, accounting for the role of institutions and policy actors in agenda setting, the role of coalitions in submitting policy positions collectively, and the polarisation of policies along ideological continuums. Each of these considerations, presented in a new set of indicators, allows to precisely measure an overlooked dimension of diversity within policy networks.