This thesis is an ethnography of the way psychologists construct their professional identities during their training in a State-funded Ecuadorian University, approached from the perspective of Critical Psychology. Considering the field´s theoretical bias, critical psychologists have called for qualitative data that contribute to ongoing discussions. Responsive to such call, this thesis asked the question: "How do psychologists in contemporary Ecuador construct their professional identity?" The author conducted a twelve-month critical ethnography, focusing on a particular training facility as a strategic site; from there, the inquiry extended to so-called "vulnerable" and "marginal" places, where trainees performed their preprofesional and professional roles. Findings highlight how the negotiation of professional identity is a "messy", subject-dependent and context-dependent process shaped by power. Trainees dwelled between the coloniality of hegemonic psychology, and a - mostly veiled - cultural resistance to it. They embodied a "dual belonging", being members of "professional" and "popular" worlds simultaneously. Trainees learned a "help-as-war" metaphor: utilising foreign theories and methods to help allegedly ignorant and in-deficit subjects, even if this implied disrespecting their culture and needs. To unpack the local professional - popular interactions which shape - and are shaped by - professional identity, the author suggests the working category of "liminal exchanges", which integrates classic Freirean conceptualisations with relevant anthropological insights regarding gift giving. Findings stress the need to construct a more critical psychology training, one which acknowledges the "messiness" of professional identity and responds more congruently to the culture and needs of the people. This would require in-group and intergroup processes of conscientización; reinforcing our commitment with social justice while avoiding unfruitful purism; accepting enabling contradictions; and articulating the fight for structural transformations with small-scale performative changes. The ethnographic evidence presented in the thesis has significant implications for ongoing debates within Critical Psychology and related fields, at a local and global scale.