. Background: The urban transport system is a complex network involving various stakeholders, each with distinct roles and objectives. Consequently, the tasks of local authorities regarding urban transport are becoming increasingly challenging, especially with the growing focus on sustainable development. Methods: This paper aims to define the key functions of urban transport organizers that significantly impact environmental sustainability. The primary goal is to assess the importance and impact of urban transport organizers in enhancing environmental sustainability in Tricity (Gdansk, Gdynia, and Sopot). The study, conducted in 2022, engaged a range of Polish stakeholder groups, including urban transport organizers from Tricity's public transport companies, local authorities, freight transport companies, and local residents. A total of 342 observations were collected using Paper-and-Pencil Interviewing (PAPI), In-Depth Interviewing (IDI), and Computer-Assisted Web Interviewing (CAWI) methods. Results: The study reveals a differentiated impact of urban transport organizer functions on environmental sustainability indicators. The most significant influence comes from financial, infrastructural and space management functions. Conclusions: Improving processes related to passenger mobility and urban freight transport is particularly complex yet essential for sustainable urban development. Integration processes in urban transport, occurring at different levels and in various areas, can unify all aspects of city transport management without distinguishing between types of transportation.