Issue d'un contexte professionnel, cette thèse tente de mettre au jour, principalement à travers le concept d'activité et la médiation du processus d'autoconfrontation, l'émergence de questionnements majeurs au cœur de la pratique quotidienne des chargés d'insertion des travailleurs handicapés en centre de réadaptation professionnelle. Il s’agit de contribuer à montrer et comprendre comment ces professionnels interrogent leur posture dans leur travail d'insertion, pris entre des valeurs parfois contradictoires, entre marché du travail et accompagnement médico-social. / This thesis draws upon a professional context in an attempt to highlight the emergence of major queries central to the everyday duties of vocational project managers supporting disabled workers in vocational rehabilitation centers. The underlying approach is based on the concept of activity and mediation through the process of self-confrontation. The objective is to help demonstrate and understand how these vocational professionals, despite being caught between sometimes conflicting values, between the labour market and the medico-social support they provide, perceive their position as they strive to enable disabled persons to find employment.