The number of students with mental health disorders (MHDs) in postsecondary institutions is increasing. Teachers' attitudes are among the main factors that influence these students' academic success. Unfortunately, their attitudes are little studied, in part because of lack of validated scales. Therefore, this article has two purposes: (1) analyse the construct validity of new scales assessing teachers' attitudes, as well as existing scales without an established construct validity; and (2) report the correlations between the variables assessed in these scales, with a special focus on two variables: (a) teachers' negative attitudes; and (b) the measures offered to students by teachers. The participants are 232 teachers from 16 French and English CEGEPS in Quebec, Canada. The questionnaire includes three scales created by the research team and three scales from the "Mental Illness Awareness Survey." Correlational and factor analyses were conducted. The scales present good construct validity. Four variables were associated with the two variables of interest: confidence in one's ability to convince a student to seek help; familiarity with MHDs; knowledge and understanding of MHDs; favourable perception of the accommodations offered by adapted and psychosocial services. Based on these results, strategies are proposed to improve teachers' attitudes.