We investigate patterns in platform ecosystem emergence. We find that the processes of ecosystem emergence—value discovery (designing and establishing an ecosystem value proposition and individual value offerings), collective governance (regulation of participation), platform resourcing (resource acquisition for set-up and scale-up), and contextual embedding (legitimation of the ecosystem in the wider societal and competitive context)—exhibit characteristic patterns as an ecosystem establishes itself. We also find that collective governance patterns vary considerably across cases and argue that early governance decisions significantly influence subsequent evolution of an ecosystem. Furthermore, we show that although there are similarities in ecosystem emergence at the macro level (during launch, expansion, and establishment), at the micro level these processes coevolve giving rise to idiosyncratic patterns of coevolution.