Purpose: This study developed an online lesson study, investigated teacher professionalism after following an online lesson study and examined students' environmental literacy. Design/methodology/approach: This study used a mixed-method research design. The qualitative approach entailed observing science learning focussing on environmental issues during Zoom meetings and interviews with teachers to gain insight into the online lesson study design. The quantitative approach involved testing learning outcomes, focussing on students' environmental literacy after one year of learning science by integrating environmental issue. Findings: The result reveal that the online lesson study design is both asynchronous and synchronous. The teachers' teams asynchronously conduct the planning sessions. The implementation, observation and discussion sessions are conducted synchronously using an online meeting platform. Analysis of online learning during the lesson study shows that mind-on activities are performed using an online meeting platform. By contrast, hands-on activities are performed asynchronously with homework assignments. The relationship between teachers' participation in lesson study and students' environmental literacy acquisition is positive. To improve the students' environmental literacy, online or hybrid lesson study in the future should synergise with environment-based co-curricular activities and science learning using a problem-based approach. Research limitations/implications: The limitations of this study are linked to the research subjects, who were situated in South Tangerang, an urban area in Indonesia. The outcomes may differ if the teachers and students are situated in rural areas. Additionally, an online lesson study was conducted during the COVID-19 pandemic, when Indonesia was under lockdown. Consequently, students and teachers must be required to engage in remote learning from their homes using digital devices. Online teaching has caused suboptimal environmental literacy among students (64.55 ± 9.04), especially in terms of knowledge, skills and participation. Therefore, it is imperative to strategize for an enhanced teaching approach towards environmental issues in the classrooms. Teaching methods that actively engage students with their surrounding environment positively affect their environmental knowledge and awareness (Kalyanasundaram et al., 2024). In future lesson plans, educators should create learning activities within the classroom (intra-curricular) and involve family members at home (co-curricular). It is pivotal to incorporate tasks into online teaching that facilitate direct interaction between students and nature to shape their attitudes, behaviours and concern for the environment (Douglas et al., 2024). Practical implications: This study's practical implication is that integrating environmental issues with science learning by framing them as crucial problems for students significantly influences students' environmental literacy. Teachers strive to meet environmental education objectives that encompass knowledge, awareness, attitudes, skills and participation. Furthermore, teachers use problem-based learning to further improve their students' environmental literacy. Originality/value: This study focuses on an analyses of an online lesson study design for science learning integrated with environmental issues. It examines the direct impact of online lesson study on increasing teacher professionalism and its influence on students' environmental literacy.