There has been a growing demand for evidence-based interventions to help students prepare for the transition between university and the world of work. The aim of this study was to investigate the effects of a career counseling intervention, in groups and online, on the career adaptability resources and perceptions of professional development and employability of college students in the final stage of their undergraduate courses. The study was based on career construction theory and the theoretical model for professional development of college students. As a preliminary activity, the intervention was performed with a pilot group (n = 20), followed by the actual experiment with an IG (n = 14) and an N-TG (n = 14). Based on a detailed protocol, the intervention was applied for three months, with six weekly sessions and a follow-up session one month after the end of the intervention. Between the sessions, the participants were expected to accomplish directed tasks. Two observers were part of the experiment and elaborated reports of each session. The Linear Mixed Regression Model (LMM) and the Jacobson and Truax (JT) Method were used to evaluate the effectiveness of the intervention, comparing each participant with themself before and after the intervention. The results show that career counseling with graduating college students expands their career adaptability resources, and their perceptions of professional development and employability. The no-treatment group did not present an increase in the score's dimensions over time. Therefore, based on the study, career counseling interventions can be recommended for college students to promote proactive action to anticipate barriers and increase awareness of possibilities and work interests among participants.