Abstract: This study investigates the influence of English language usage on students’ academic performance in Physics at public secondary schools in Gakenke District, Rwanda. The specific objectives include assessing students’ academic performance in Physics and examining the relationship between English proficiency and Physics performance in these schools. A descriptive research design employing both quantitative and qualitative methods was utilized, with questionnaires as the primary data collection tool. The target population comprised 1,839 individuals, including 138 administrators, 223 teachers, and 1,478 students from public secondary schools in Gakenke District. A sample of 329 participants was selected using simple random sampling for teachers and students, and purposive sampling for administrators. Data were analyzed using SPSS Version 21 and Microsoft Excel, applying descriptive statistics. Results indicated that 67.8% of respondents disagreed that English was frequently used in classes, and 66.7% felt students lacked strong English skills. Additionally, 91.8% of students expressed dissatisfaction with their academic performance in Physics, while 70.2% reported low engagement in hands-on experiments. Correlation analysis revealed a significant correlation between English language usage and students’ academic performance in Physics (r=0.721, p=0.000). The findings suggest a decline in Physics performance linked to insufficient English language proficiency. The study recommends that the Ministry of Education develop and implement policies that prioritize English language proficiency as a key component of the national curriculum, particularly in science subjects. This includes providing resources and training for teachers to effectively integrate English language instruction into their teaching of Physics and other subjects, ensuring that students are well-equipped to succeed academically in an English-speaking environment.