Students’ performance in science subjects has often been associated with lack of conceptual understanding (Matriculation and Secondary Education Certificate Examination Board, 2018). Research shows that in countries where the language of instruction is different from the students’ home language, this has an impact on their conceptual understanding as well as on their performance in formal assessments (Charamba, 2021; Charamba, 2020a). This study was carried out in a secondary state school in Malta, where both English and Maltese are official first languages, but Physics is taught and assessed in English. It involved action research where, as a Physics teacher, I implemented a number of inquiry-based activities with one group of my students at the secondary state school where I taught. The group was composed of five students: a foreign student who understood Maltese but spoke solely in English, two first language Maltese speakers proficient in both Maltese and English and considered parallel monolinguals, and two first language Maltese speakers with low proficiency in English and hesitant when expressing themselves in English. When inquiry-based learning activities were implemented in the first cycle with strict use of the English language, I observed that the students struggled to express themselves. In the second cycle I still used inquiry-based learning activities but encouraged the students to express themselves in their preferred language (English, Maltese or code-switching). From my analysis I could conclude that when the students were allowed to speak in their preferred language, they often resorted to Maltese and code-switching. Their contributions towards the discussions increased in frequency as well as in the quality of their insights when attempting to provide sophisticated explanations. This study has shown that adopting inquiry-based learning approaches where my students spoke in their preferred language helped them to express deeper meanings. This study concludes that in a bilingual context like Malta, learning science in one’s second language was a hurdle for my students. However, they also became more aware that they need to learn how to express themselves well in English when talking physics. These results highlight how language impacted my students’ learning, and that as their teacher I had the responsibility to teach the language of science together with conceptual understanding.