The article examines the capabilities of content-based instruction (CBI) within the system of professional training of future officers of the State Border Guard Service of Ukraine, specifically within the online English for Specific Purposes (ESP) course. The authors argue that nowadays, due to the quarantine restrictions and ongoing war initiated by Russia, it is crucial to enhance the border guards’ foreign language competence through a distance learning system. The study showed positive results in applying the CBI strategy to deliver an ESP course. This approach contributes immensely to developing context-appropriate language competence, boosts motivation-driven engagement, and increases retention and long-term academic success rates. The course content includes such topics as intercultural communication, illicit trafficking of radiological and nuclear materials, human trafficking, and fundamental rights. To deliver the content of the CBI course, the authors had to consider its online format and work out such learning activities as reading and listening to authentic job-related content, completing online interactive activities, and engaging in case-studying and problem-solving activities. The course results showed a considerable improvement in learners’ ability to effectively communicate in English within the professional border guard context, use the foreign language to build knowledge and skills around human values, recognise, analyse, and solve various border-related incidents involving topics covered in the course. The effectiveness of the online ESP course studied based on CBI has shown that implementing this approach in online education deserves recognition and acceptance.