Abstract Background A first approach addressed to ascertain whether emotion regulation (ER) could be a transdiagnostic construct between eating disorders (EDs) and gambling disorder (GD) (through a joint clinical clustering analysis of both disorders) was performed by Munguía et al. (2021). Both conditions were represented by a severe, moderate, and low ER profile subgroups, according to the degree of ER difficulties. Results showed a linear relationship between the severity of ER difficulties and the severity of the disorder and the psychopathological state. Aims Based on the aforementioned cross-sectional study, the objective of this longitudinal research was to explore the treatment response of the different ER subgroups. Methods 459 adult patients (n = 277 ED; n = 182 GD) were included. Several clinical variables, as well as outcome indicators (after completing 16 weeks of cognitive-behavioral therapy), were evaluated. Results The three subgroups found in the previous cross-sectional study were taken for the performance of the present research. ED and GD distribution in each subgroup replicates the one exposed by Munguía et al. (2021), as well as their characterization, considering psychopathology, disorder severity and personality traits. The low ER subgroup reported a better response to treatment, whereas the severe group had the highest rates of non-remission and dropouts. Conclusions Our results suggest that greater difficulties in ER lead to poorer treatment outcomes. Therefore, tailored treatments for patients with poor ER abilities would be recommended to improve adherence and treatment outcomes.