The sustainability of an organization depends not only upon its financial performance, but also upon its environmental and social performance requiring the integration of economic, environmental and social objectives i.e., the triple bottom line (TBL) into overall strategic plan and decision making process. This research introduces a new decision making tool that integrates both financial and nonfinancial performance measures into the process of investment planning via the TBL. It makes use of stakeholder theory for group decision making, analytic network process (ANP) as a decision support tool and stochastic linear programming to create an optimal investment portfolio. This new tool evaluates and prioritizes a set of projects and creates a long-term balanced investment portfolio based upon the perspectives and priorities of the stakeholder groups and decision makers. It can assist decision makers with developing and making proactive decisions which support the strategy of their organization with respect to economic, environmental and social issues, ensuring the sustainability of their organization in the future.