The paper deals with the leadership importance and the role of teams in the business application improvement project. A team consists of a certain group of people who have the same goal and work together to achieve that goal. Many experts believe that teamwork is the best way of organizing work, and that this form of work will be the most widely used in the future. Successful project teams are focused on the tasks that need to be solved. Adequate team management plays a key role in the successful completion of the project. Teams that are well organized, motivated, have clear goals and good communication achieve better results on the project. Also, cooperation within the team, management support and continuous training of team members play an important role in the success of the project. A key role in developing the team is played by the project manager, who should have highly developed management and communication skills. Every manager has his own leadership style, and it is achieved as the final outcome made up of a combination of his knowledge, experience, traits and skills. The project manager should coordinate team activities, assist team members in performing tasks, create conditions for good communication within the team, encourage and improve team integration. Each team member is assigned his team role based on his preferences. Belbin states that there are eight roles in a team, and they are the researcher, the creative, the encourager, the coordinator, the evaluator, the implementer, the finisher and the team builder. The behavior of team members is based on personality traits that have an impact on team harmony, communication, balance when performing work tasks, and team efficiency. The paper describes a business application improvement project in which team members participate, each of whom has a specific role. By carrying out their daily tasks, it leads to the successful completion of the project. Team members communicated through Microsoft Teams and SharePoint virtual tools that enabled them to master their daily work more easily.