This article examines anti-missionary rumors that prevailed in nineteenth-century China and led to the Tianjin Missionary Case of 1870. Relying on archival sources, it shows that many rumors were fueled by Protestant missionaries’ medical practices in addition to political conflicts. Furthermore, the rumors were framed in spatial concepts. The rumors arose and persisted not because the missionaries deliberately hid information, but rather because the visibility of their daily activities, the accessibility of the space they inhabited and practiced in, and the spatial placement of their living quarters contradicted cultural norms in nineteenth-century China and therefore prevented the Chinese from acquiring correct information about the missionaries. The ambiguity of information that caused the rumors was the result of the confrontation between two ways of understanding space.