Online English Language Teaching (ELT) places substantial cognitive, emotional, and technological challenges on teachers, intensifying their probability of burnout. Using an explanatory sequential mixed-methods design, this study explored whether conscientiousness accounts for teachers’ potential to cope with perceived instructional load and prevent burnout in online English as a Foreign Language settings. Ninety-two full-time online EFL instructors completed the Maslach Burnout Inventory (MBI), the Big Five Inventory (BFI), and an adapted Workload Perception Scale (WPS). Hierarchical regression indicated that perceived instructional load was linked to burnout (combination of emotional exhaustion and depersonalization; R² = .31, p < .001) and that conscientiousness autonomously enhanced prediction (β = –.35, p < .001; ΔR² = .12), showing lower burnout among more conscientious teachers. Correlational analyses supported negative correlations between conscientiousness, perceived workload, and burnout symptoms. Follow-up semi-structured interviews with 15 teachers selected purposively found three resilience practices which were typical of highly-conscientious instructors—structured planning, clear work-life boundaries, and digital organization strategies—that proved to influence workload evaluation. The integrated quantitative and qualitative findings suggest conscientiousness serves both as a predictive quality and a behavioral capacity for maintaining teacher well-being in highly demanding digital settings. Implications for teacher training consist of incorporating personality-sensitive training in managing time, digital self-regulation, and boundary context.