In Québec (Canada), vocational training centres hire their teachers based on their occupational skills and knowledge. Often without prior pedagogical training, teachers must complete a bachelor university degree including three or four internships. Conducted in their workplace, novices are then accompanied on-site by an assistant teacher (AT). Untrained for this role, there are little to no measures to support ATs in these additional tasks. Based on the testimonies of 15 ATs, this paper aims to expose the motivating factors and perceived benefits of performing this role, and how this plays an important part in the development of competent action and performance. To extract meaning, a qualitative methodology was used, and semi-inductive logic technics were applied. The results detail the ATs' experience in providing support to interns, as well as enlighten the facilitating and limiting factors to their "competent action using desire to act" theories.