Group transdiagnostic cognitive-behavioral therapy (CBT) offers a promising solution for limited mental health access in Portugal. Understanding barriers to patient adherence is crucial for successful implementation. This study aimed to characterize the prospective acceptability and preferences for unified transdiagnostic CBT and group therapy in the Portuguese general population and explore their correlates. A sample of 243 participants (18–88 years old), recruited online, completed an online survey collecting information on sociodemographic and clinical characteristics, acceptability of transdiagnostic CBT treatments, specifically of Unified Protocol (UP), acceptability of group therapy, therapeutic format preferences, beliefs about group therapy and help-seeking attitudes. Most participants were receptive to and perceived as useful both unified transdiagnostic CBT and group therapy. Overall, participants presented significantly more favorable attitudes than unfavorable attitudes toward unified transdiagnostic CBT and group therapy (p < .001). Multivariate analyses revealed that (1) favorable attitudes toward transdiagnostic treatments were negatively associated with being employed and positively associated with living in an urban area, and higher efficacy scores; (2) unfavorable attitudes toward transdiagnostic treatments were positively associated with being married/cohabitating and negatively associated with vulnerability scores; (3) being female, living in an urban area, and higher efficacy and myth scores emerged as positive predictors of favorable attitudes toward group therapy; and (4) efficacy and vulnerability scores and help-seeking propensity emerged as negative predictors of unfavorable attitudes toward group therapy. These findings highlight the importance of delineating strategies to increase knowledge and acceptance of unified transdiagnostic CBT and group therapy in the Portuguese population, addressing specific individual characteristics.