The difference in personality traits between men and women have been documented, however, few studies focus on the changes after psychotherapy. This study compares personality traits of college students who attended group psychotherapy for 12 months, analyzing changes and differences between men and women. A quasi-experimental study was carried out with two measurements in a single group. In the basic scales, women decreased F (Z = -2.33, p = .020), Hs (Z = -2.80, p = .005), Pt (Z = -2.02, p = .044); men decreased D (Z = -3.03, p = .002) and IS (Z = -2.13, p = .033). In content scales, women had changes in DEP (Z = -2.55, p = .011), SAU (Z = -2.42, p = .016) RTR (Z = -2.12, p = .034); men in BAE (Z = -2.03, p = .043), DEL (Z = -2.14, p = .033), FAM (Z = -3.07, p = .002) SAU (Z = -2.34, p = .019). In the supplementary scales, women decreased in A (Z = -2.10, p = .036), Dpr (Z = -2.31, p = .021) EPK (Z = -2.74, p = .006) GF (Z = -2.12, p = .028); men in C (Z = -1.97, p = .049), GF (Z = -2.12, p = .034) and R (Z = -2.17, p = .030), tending to improve in the scale A-MAC (Z = -1.89, p = .059). Group psychotherapy offers positive changes in patients' personality traits and seems to have different effects regarding each gender.