ABSTRACT Medan is a port city in Sumatra, Dutch East Indies, developed in the late nineteenth and early twentieth centuries. A special case among colonial cities, it featured a large number of Chinese migrants – a third party in addition to the colonizer and the colonized – who played a key role in its urbanization process. Highlighting a trichotomous power framework formed by the Dutch colonizer, the indigenous people and the Chinese diaspora, this paper argues that the Chinese diaspora, with the arrival of commercial elites, obtained opportunities to shape the backbone of the city through skilfully transforming their economic power into political and spatial power. Chinese economic activities such as property investment and co-development not only led to unconventional Chinese quarters but shaped the zoning and axiality of the whole city. The Chinese diaspora also shaped Medan’s streetscape and architecture through individual building design, which, in turn, strengthened their economic power by the careful manipulation of architectural elements from various sources to suit different purposes. The planning history of Medan represents an alternative trajectory to colonial urbanization often led by Europeans, highlighting an ambiguous and shifting power relation among three parties in a transforming colonial society.