This thesis addresses the question “How and under what conditions does temporary urbanism emerge and develop within the transition phase of Dutch brownfield redevelopment toward long-term use?” While its capacity to activate vacant sites is widely acknowledged, the processes through which it emerges, evolves and anchors remains poorly understood. Through a comparative multiple-case study of four Dutch brownfields, drawing on document analysis, field observations, and eight stakeholder interviews, this research employs a two-stage analytical framework. First, each site’s initial activation is categorized as either unstructured (coincidental, grassroots driven) or strategic (policy-embedded, facilitated). Second, strategic trajectories are traced through the lens of an existing three-phase model Test, Growth, and Development, adding an initial “Coincidental” phase to capture informal grassroots activations. A complementary nine-condition framework (encompassing location, physical and environmental factors, ownership, regulation, finance, socio-cultural context, risk perceptions and interim utilization is then applied to identify enablers and barriers to temporary urbanism. Findings reveal that three sites (Centrale Harculo, Locatie Sportlaan and Bajesdorp) successfully transitioned through all four phases, progressing from ad-hoc, bottom-up activations to small-scale trials, investment-driven scaling, and ultimately strategic integration into long-term redevelopment. In contrast, Landgoed Steenenburg remained mired in the Coincidental phase for nineteen years, sustained only by informal anti-squat housing and intermittent events, due to financial, ecological, and governance constraints. Across all cases, factors such as site location, regulatory context, ownership structure and socio-cultural dynamics alternately facilitated or hindered temporary uses. Moreover, supplementary conditions, including ownership orientation and site image, proved critical in embedding temporary urbanism within broader development ambitions. The study concludes that temporary urbanism delivers enduring value only when it is purposefully embedded within formal redevelopment processes. Key prerequisites include a clear long-term vision from the landowner, timely and coordinated decision-making and an engaged intermediary actor to bridge interim activities with permanent development goals.