Background: Although a great deal of research has been undertaken from 1982 on TGfU, teachers consider its implementation to be complex and are reluctant to integrate it into their teaching practice. Furthermore, some TGfU literature does not suggest how it might be implemented and how problems might be overcome. On the other hand, a review of TGfU studies showed three shortcomings. First, most of them only compared TGfU with a technique-based approach in the school setting. Second, the studies did not follow the fidelity guidelines for models-based practice research and it is therefore difficult to contrast their results. Third, lesson design was not aligned on the principles of play. Thus, this study provide additional support for going forward from comparative studies in educational settings, and enacting an aligned TGfU unit of floorball contextualized in the principles of play. Purpose: To verify whether pupils improved in variables related to performance and adherence after the enactment of an aligned TGfU unit. Method: An eight lessons unit was designed, validated, and enacted using a mixed-methods quasi-experimental pre-test and post-test design. Participants were 41 pupils (23 boys and 18 girls; M = 11.73, SD = .66 years old) from two regular physical education classes with the same teacher. The teacher was trained in the TGfU approach. In pre-test and post-test assessments, data from decision-making, technical execution, cover, support, game performance, game involvement, enjoyment, perceived competence, and intention to be physically active were collected, using the Game Performance Assessment Instrument, two psychological scales, and two focus groups interviews with the pupils and the teacher. We analysed quantitative data using t-tests and qualitative data following an open and axial coding based on the pre-existing categories. Results: Pupils improved in decision-making, technical execution, cover, support, game performance, game involvement, enjoyment, perceived competence, and intention to be physically active after implementation of the TGfU unit. The pupils and the teacher perceived improvement in all the variables analysed as a consequence of the intervention. Conclusion: After the implementation of the aligned TGfU floorball unit, pupils improved in the variables related to performance and adherence. Based on participants' key comments, four aspects appeared to be essential for the success of the unit: (a) the lesson design; (b) collaboration from planning to teaching the unit between the researcher and the teacher; (c) the inclusion of learning tasks linked with cover and support; and (d) the use of two reflective periods that helped pupils to understand and apply new knowledge.