Preoccupied with French mission agitation in the late 1850s and during the Franco-Spanish invasion of southern Vietnam, scholarship has long neglected the dramatic change taking place in preceding decades at the local level between Catholics and mainstream society. Exploring negotiation between Catholic communities and authorities, as well as organisational shifts in mission activity, this article brings into sharper focus the turmoil of the late 1830s and 1840s Nguyên repression of Catholicism.