Social learning in collaborative processes is considered important for addressing complex natural resource dilemmas and for supporting multi-actor interactions in joint problem framing, and the co-construction of solutions. While social learning is often presented as a normative approach for stimulating shared understanding among multiple actors, little is known about how long-term emergent social learning processes occur. In this paper, we analyse a long-term emergent social learning process within transboundary river basin management. To this end, we apply the concept of the learning space - meaning arenas for interaction, deliberation and reframing - as a lens for evaluating emergent social learning processes. Results show that in the Zambezi Basin, social learning in emergent processes occurs in stages and is triggered by various factors that result in collective outcomes throughout the process. Emergent social learning processes were triggered by structural reorganization processes, natural calamities, the influences of cooperating partners and international frameworks. Over time, the spaces for interaction and deliberation led to the reframing of basin management practices and the subsequent development of new institutions. In addition, social learning outcomes included increased relational capacities of national and regional actors and trust, but also mistrust and power issues. While emergent long-term processes are difficult to evaluate, our findings reveal that the concept of the learning space provides a structure for assessing long-term emergent social learning process outcomes, and thus, can provide a broader understanding of processes needed in designing long-term management practices or institutions.