Collaboration between researchers has been shown to influence their productivity and scientific impact. Although these ties have been widely discussed in the literature, the nature of the co-authorship networks between the most successful scholars remains a question. To provide an answer, this study conducts a cross-case analysis of the collaboration networks between Highly Cited Researchers, focusing on the research output and co-authorship patterns in Highly Cited Papers across three award categories: Clinical Medicine, Materials Science, and Social Sciences. Our findings indicate that there are category-specific differences in publication output and the intensity of collaboration between Highly Cited Researchers. Notably, Highly Cited Researchers in the Social Sciences demonstrate a less collaborative approach to research than those in Clinical Medicine and Materials Science. While Highly Cited Researchers in all three categories featured interconnected collaboration networks among themselves, those in Clinical Medicine and Materials Science exhibited a more collaborative environment, while those in Social Sciences showed a tendency towards independent research efforts. The case of Social Sciences is further evidenced by higher fragmentation within the collaboration network of Social Sciences, indicating a less cohesive collaborative framework. The analysis of the Giant Component—the largest cohesive subset of the network—revealed that it is less representative of the overall network structure in the Social Sciences than in Clinical Medicine and Materials Science. Finally, the centrality measures indicated that Highly Cited Researchers with high betweenness and closeness centrality act as crucial bridges within each network, significantly shaping the structural cohesion and collaborative dynamics of their respective fields.