This study aimed to compare the effectiveness of online group therapy based on emotional schema therapy with that of transdiagnostic therapy in improving distress tolerance and cognitive emotion regulation among university students with adjustment disorders due to romantic break-ups. The statistical population included all students who experienced a romantic break-up in Iran in 2020, aged 18–38 years. Due to COVID-19 pandemic restrictions, participants were selected online. After filling in initial forms, diagnostic interviews were conducted through purposive sampling. A group was then randomly selected and divided into three groups: the first experimental group (transdiagnostic group therapy) included 15 participants; the second experimental group (emotional schema therapy) consisted of 15 participants; and the third group was the control group with 15 participants. The experimental groups received ten 90-min group therapy sessions. Participants completed the Distress Tolerance Questionnaire and the Cognitive Emotion Regulation Questionnaire at pretest, post-test and 1-month follow-up stages. According to the results of repeated measures ANOVA, there were significant differences between the experimental and control groups (p < 0.05) in the post-test scores of distress tolerance and cognitive emotion regulation strategies. However, there were no significant differences between the two experimental groups. The results indicated that both internet-based transdiagnostic group therapy and emotional schema therapy were effective interventions in mitigating symptoms of adjustment disorders due to romantic break-ups among university students. This highlights the potential of online group therapy as a viable option for students experiencing such disorders, particularly during pandemic-related restrictions.