This research examines the nature and the significance of Intercultural Competence of Foreign Language Assistants (FLA) in Central Mexico, Guanajuato, during a 10-month Assistantship programme. By inquiring, interviewing and observing four groups of participants (a former cohort of FLAs, educators, students and  current FLAs), this study clarifies the process of understanding and acquiring intercultural competence encouraged by a periodic, critical and (auto)reflective intervention. In this research, different approaches are implemented, combining quantitative and qualitative methods using questionnaires, semi-structured interviews and focus group sessions. A Professional Development Programme (PDP) was established to guide FLAs throughout the assistantship to support them in reaching their personal and professional goals and, to understand and embrace the intercultural perspective of the experience. Literature evidences several practitioner-oriented approaches identifying problematic areas, implementing empathic attitude and suggesting solutions (Paul, 2009; Pollard, 2008; Schön, 1983). In this study, a customised framework contributes to data collection process including testimonies, statistics and self-assessment (Richards, 2005; Argyris and Schön, 2002; Huberman, 1989). The findings, both the quantitative and qualitative aspects, demonstrate that through a constant and personalised PDP assistants have gained intercultural awareness and acquired abilities in presenting and facilitating cultural practices to the students. In addition, this programme serves to raise educators’ awareness about the roles of FLAs and the way these groups of participants could work together to support learners by identifying and integrating cultural knowledge to French as foreign language (FFL) learning.