Background. Modeling architectural aspects of the system is an essential activity in software development. Inthis context, developers work in parallel, and collaborate to define application software models, such as classdiagrams. Problem. Although many software modeling tools have been proposed, there is a lack of distributed collaboration features. Solution. This study proposes C-SAMT, a web tool for collaborative modeling of UML class diagrams. Developers can benefit from using C-SAMT when performing modeling tasks, such as creating domain models in parallel, and collaboratively. Evaluation. We recruited 20 industry professionals to perform a qualitative evaluation of the tool through a questionnaire. Results. Majority of Industry professionals (85%, 17/20) reported that totally agree that the communication channel of the tool worked properly, they also (80%, 16/20) totally agreed the models generated collaboratively with C-SAMT had small numbers of conflicts, and they also (90%, 18/20) perceived improved productivity gains using the proposed tool. Conclusion. C-SAMT provided a collaborative environment, which were positively evaluated by developers, who reported that C-SAMT had a good communication channel between team members.