Objective: To report how improvements on a Brazilian language intervention for early childhood education settings (PROLIN) were made and evaluated. Study Design: In the first phase, the programme layout and materials were improved. This involved redesigning the guidelines for the programme, adding videos (using a learning management system) and creating an observation checklist to monitor the fidelity of implementation. The second phase was a two-week pilot study (a seven-session intervention) involving two teachers and 22 students. Checklists and video footage were analysed to investigate implementation. Results: Quality of implementation was generally good, but we identified additional areas for improvement. Teachers had some difficulties with aspects related to session dynamics, implementation of activities and use of techniques that reinforce learning. Conclusions: The pilot study was instrumental in identifying obstacles for a scaled-up, high-quality implementation. The design of these materials took into consideration ways of guiding and supporting teachers to: (1) offer students adequate participation time; (2) help include children who are shy or have behaviour problems; (3) use teaching strategies properly; (4) bring sessions to a close; and (5) reach the objectives of each session. Further modification is still needed, especially in the manual, videos and supplementary materials.