The ability to communicate orally is important in science, but few tools assess students’ perceptions and attitude toward scientific oral communication in scientific programs. This research developed the Perceptions and Attitude toward Scientific Oral Communication (PACOS) questionnaire for post-secondary students with the theoretical model associated. A sample of 1295 Quebec college students in the natural sciences program participated in this research, responding to the three versions of the questionnaire during the stages of its development. Principal component analyses (PCA) followed by a confirmatory factor analysis (CFA) allowed to identify five factors for the perceptions and attitude toward scientific oral communication questionnaire: pleasure, anxiety, perceived relevance, and two aspects of self-efficacy (S-EOCS), namely the S-EOCS “Norms & Content”, which relates to the effectiveness in expressing oneself orally, and the S-EOCS “Showmanship”, which describes rather how to be dynamic and capture the attention of the audience. The overall evaluation of the PACOS shows that this questionnaire has good psychometric qualities and that the components obtained during the validation process support the theoretical model.