The purpose of this qualitative study is to describe the experiences of preschool children, families, and teachers related to the project approach implementation in the context of disadvantaged conditions. The research design included a synthesis of a case study and action research. Using purposeful sampling methods, the participants included 3-6-year-old children, their families, and the staff in a preschool, serving disadvantaged children. The action plan included the implementation of the project approach. Multiple data collection techniques included the use of semi-structured interviews, observations, the researcher journals, and obtaining various documents. This research uses data relevant to project implementation from a comprehensive data set collected over a year. Data analysis employed inductive methods using ATLAS.ti 7 software. Findings show that the project approach supported the teachers’ professional development. The teachers have partially adopted some educational practices they have learned during the project implementation. However, they were resistant to implement the project approach as a whole during the academic year. Disadvantaged children exceeded the expectations of the teachers and exhibited social-emotional, cognitive, and language gains during the project. Families also increased their educational awareness and quality interactions with their children. Changing some implementation features to reduce time and workload for teachers, offering resources, using on-site approaches for in-service training, supporting teachers may motivate them to implement the project approach.