Background/Objectives: The accelerating global concern for the mental health of university students necessitates delivering intervention programs. The purpose of this study is to evaluate the effectiveness of a 5-week blended counseling group program, with two integrated approaches, positive psychology intervention and cognitive therapy, toward undergraduate engineering students' depression, anxiety, and stress, from the Higher School of Pedagogical and Technological Education, Greece. Methods: Participants with a mean age of 21.12 (SD = 3.68) were administered the DASS-21. A two-way repeated-measures design was used and the two factors were condition and time. The subjects underwent two conditions, the experimental (n = 40), consisting of the civil and mechanical engineers, and the control (n = 52), that encompasses the electrical engineers. The three dependent variables, DASS-21 factors, were measured at three time points, at the beginning of the program, midway through the program, and at the end of the program. Results: The effect of the interaction between time and the conditions on DASS-21 depression and stress was significant. In particular, the experimental subgroups showed lower depression and stress at the end of the program in comparison with the control group. However, they did not demonstrate significantly lower scores on anxiety. Furthermore, the two intervention subgroups did not exhibit any significant mid- and post-test differences on all measures. Conclusions: In light of the obtained results, it can be concluded that the group counseling blended cognitive positive psychology program is an effective intervention.