This study examines the effectiveness of Content and Language Integrated Learning (CLIL) implementation in science subjects and reports on the challenges that content teachers encountered during CLIL instruction. In addition, the study attempts to investigate students' perceived knowledge of and satisfaction towards the implementation of CLIL. To accomplish these goals, relevant CLIL instructional materials were developed by the researchers and subject content teachers. Content teachers received training in English to apply the designed material and implement the CLIL instruction prior to CLIL classes. A convenience sample of 24 university students participated in this study. They were required to write research abstracts and reports in English according to the knowledge of genre and move-based structure. The data collection was conducted using a mixed qualitative and quantitative method. Student abstracts written in English were also analysed qualitatively to investigate the use of linguistic features, structural elements, and vocabulary. Additionally, six subject content teachers and six students were interviewed about their perceptions of and challenges from CLIL implementation. Student questionnaires about their attitudes towards CLIL implementation were then used to collect quantitative data. Over the seven weeks of CLIL lessons, the interview results revealed that close collaboration between content and language teachers prior to CLIL implementation was necessary to affirm the steps and procedures to be applied in the classroom. Some of the content teachers conveyed the importance of advancing students' language-related knowledge in expressing scientific ideas in English. Most students also expressed their satisfaction towards CLIL instruction as it facilitates the learning process, helping them improve their writing and reading skills as well as their ability to use academic vocabulary. The findings of this study advance our understanding of how to implement CLIL lessons, including the importance of CLIL-related training, creating instructional materials, and language integration of content and language learning in science at the university level.