The 18th biannual International Planning History Society (IPHS) conference took place 15–19 July 2018, in Yokohama, Japan. Themed ‘Looking at the World History of Planning’, the conference asked to enhance and promote the diversity of perspectives and narratives existing in the research of cities and their planning history (select full papers and abstracts are available for public access from the IPHS website: https://planninghistory.org/conferences/yokohama/ and https://journals.library.tudelft.nl/index.php/iphs/issue/archive). The conference consisted of diverse events, which included a pre-forum, 3 keynote speeches, a Gordon E. Cherry Memorial lecture, 68 research panels of presentations, 7 round tables, 23 book talks, as well as short and long tours. Based on a selection of relevant panels and roundtables, this report explores three prominent themes discussed in the conference: intercultural exchange, intracultural exchange and global planning history. It lays out how planning diffusion among and within cultures influenced cities and their planning and emphasizes the importance of understanding planning history from transnational and global perspectives. The choice of Yokohama, a city which has a history that embodies the impact of globalization on planning exchange, corresponded with its goals, given that it was one of the first ports that opened to trade with Western nations under the so-called unequal treaties that ended the long era of Japanese seclusion. The conference took place in the Port Opening Memorial Hall, a Neo-Renaissance building located in the former foreign trade district opened in 1917 at the 50th anniversary of the city’s port opening.