Stakeholder participation has become a vital factor in achieving environmental sustainability in development projects, especially in ecologically sensitive areas such as South-South Nigeria. This study looked into how engaging stakeholders can impact sustainable environmental results in development initiatives marked by oil exploration, biodiversity loss, and ongoing socio-environmental conflicts. The study employed participatory development theory and stakeholder theory; the research used a mixed-methods approach, gathering survey data from community members, government agencies, and corporate representatives, along with qualitative insights from key informant interviews. The findings revealed that when stakeholders are included, it boosts environmental accountability, fosters local ownership, and allows for the incorporation of indigenous knowledge into project design and execution. On the flip side, when engagement is limited or merely symbolic, it often leads to environmental harm, community backlash, and project failures. The study also highlighted that issues such as power imbalances, weak institutional frameworks, and poor communication channels can hinder effective participation. Interestingly, corporate social responsibility efforts by multinational oil companies showed varying levels of success, largely depending on how deeply they involve the community and the transparency of their processes. The research emphasised the importance of participatory governance structures that focus on equity, dialogue, and ongoing engagement among all stakeholders. Ultimately, it concludes that achieving environmental sustainability in the South-South region hinges on meaningful stakeholder involvement throughout all phases of development planning and implementation. The policy recommendations stress the need to strengthen regulatory institutions, build community capacity, and encourage multi-stakeholder partnerships to promote environmentally responsible and socially inclusive development outcomes in the area.