This case study examines the use of the Sheltered Instruction Observation Protocol (SIOP®) Model as a framework in the design of an in-service training to answer CLIL teachers' methodological needs to integrate content and language. The study also analyzes teachers' receptiveness of the use of SIOP in a CLIL bilingual program to facilitate the integration of content and language. It follows case study methodology and draws on thematic analysis to examine data collected from teacher interviews, questionnaires and observations of the training workshop. Findings showed that one of teachers' main difficulties was their lack of academic language awareness, and it is concluded that extensive professional development training drawing on some of the principles behind SIOP could assist CLIL teachers to integrate language in content classes. Teachers' receptiveness of using the SIOP concludes its suitability as a PD training to help non-language specialist teachers systematically plan for language in their content classes. However, adaptations of the Model are suggested to adjust to CLIL contexts and teachers' needs.