Needs analysis (NA) has been a core component of language for specific purposes (LSP) research and curriculum development for the past half-century, and within the past decade has seen significant methodological advancement. Specifically, certain LSP NA research has adopted task as a unit of analysis (e.g., Youn, 2018; Malicka et al., 2019), and care has been taken to further understand the language-learning needs of professional contexts through the triangulation of stakeholders and methods (e.g., Serafini et al., 2015). While North American, English-native missionaries serving in Latin America must learn Spanish in order to fulfill their professional calling, the learning needs of this population have not been empirically investigated. This study applies best practices in LSP NA to a sequential mixed-methods design. Through a sequence of stakeholder interviews and quantitative questionnaires, the study identified target communicative tasks of missionaries serving in Latin America, and determined how these tasks were described by missionaries in terms of relative difficulty, frequency, and importance to their work. The study produced an inventory of 21 target communicative tasks, as well as their characterizations, and further analyzed their difficulty, frequency, and importance according to functional role and proficiency. In addition to answering the research questions driving the inquiry, thematic analysis of interview data uncovered features of the LSP context that have bearing on future research and curriculum development, such as the need for responsiveness of the organization's language learning program to operational strategy. These findings provide a foundation for the development of a task-based curriculum that has the potential to address the lexical-semantic, morphological, and socio-pragmatic learning needs of professional missionaries serving in Latin America. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]