This chapter focuses on a data team as a Professional Learning Network. Data teams are teams of teachers and school leaders who collaboratively use data to solve a specific educational problem in their school. The focus is on school improvement and professional development in data use. The chapter explains the concept of data use or data-based decision making. Examples of data include student achievement results, student background information, surveys, and classroom observations. Data-based decision making pertains to using these systematically collected quantitative and/or qualitative data to base decisions on. The chapter describes the specific data team intervention. The data team intervention focuses on professional development of teachers and school leaders in the use of data, with the ultimate goal of school improvement. The chapter also focuses on one specific data team from Sweden. It provides the factors that can enable or hinder the work of a data team.