Sustainability is a vital strategy for manufacturing industries to address major environmental issues. Stakeholders’ growing ecological awareness is forcing manufacturers to adopt green human resource management practices (green HRM practices) and environmental management systems (EMS) to improve sustainable performance (SP). This research explores the key themes of green HRM practices, EMS, and OCBE, and how these themes affect the environment and explain SP among ISO14001-certified manufacturing firms. This research used a qualitative methodology following an interpretivist approach. It employed the thematic networks technique, using qualitative data to achieve the objectives. The qualitative data were collected using semi-structured interviews conducted with HR managers and then analyzed using NVivo 12. Thematic network analysis explores basic and organizing themes within qualitative data. Four central (parent) themes, i.e., green HRM practices, OCBE, EMS, and SP, emerged. First, green HRM was sub-divided into three sub-themes: (i) green recruitment and selection, (ii) green training and development, and (iii) green assessment and rewards. Consequently, OCBE was then sub-divided into three themes: (i) eco-helping behavior, (ii) eco-initiatives behavior, and (iii) eco-civic engagement behavior emerged. Likewise, EMS was sub-divided into three themes: (i) ISO14001, (ii) EMS key benefits, and (iii) EMS key motives. Lastly, SP was further divided into three sub-themes: (i) economic, (ii) social, and (iii) environmental. This research also discusses important implications for managers and organizations.