Instructor collaboration shapes the coherence and quality of educational programs, yet in professional continuing education it is often informal and dependent on individual goodwill. There is a research gap in how this collaboration unfolds in client-driven, modular continuing education, and how it operates in the Latin American context. This study addresses this gap by examining the pedagogical and assessment practices instructors employ in a Mexican continuing education program, as well as the factors that enable or constrain their collaboration. We conducted a qualitative case study, gathering data through six focus groups with 22 instructors. Transcripts were examined using reflexive thematic analysis, with in vivo coding consolidated into themes through collaborative, consensus-based coding. Based on Cultural-Historical Activity Theory, it was observed that informal exchanges and ongoing feedback are customary, whereas formal collegial assessments occur sporadically, limited by reluctance to evaluate beyond one¿s own discipline and by a lack of allocated time. This study's contribution is to reframe these obstacles as structural contradictions within the activity system, in which valued collaborative practices lack the rules and division of labor needed to enact them. The collaboration that does occur is motivated by a culture of affective trust that simultaneously fuels cooperation and impedes its formalization. This finding cautions against transplanting external collaboration models without adaptation.
