The work of teaching is fundamental for achieving Agenda 2030, which defends the importance of improving quality in education (Sustainable Development Goal SDG 4), gender equality (SDG 5) and responsible consumption (SDG 12). Thus, the aim of the present study was to analyse teachers’ self-perceived digital competence as regards their eco-responsible use of technology. A total of 259 teachers in Preschool, Primary and Secondary Education in the Valencian Community (Spain) completed the 14-item questionnaire designed and validated by Barragán et al. (2020). Added to this were two open questions. The data collected then underwent quantitative (descriptive and comparative) and qualitative (conventional and summative content) analysis. Notable among the results were the low levels of knowledge and training regarding the environmental impact of technologies and the use of preventive measures. In addition, differences were found as regards gender, with males having a more positive self-perception, especially those teaching in Secondary Education. The information about training they provided in their narratives supported the quantitative findings. Their voices also led to the uncovering of proposals on how to teach eco-responsible practices and attitudes regarding the use of Information and Communication Technology (ICT). Finally, teacher training was identified as the main problem but also the main solution. All efforts should therefore be directed towards training teachers in the eco-responsible use of ICT following a holistic approach to sustainability.