This paper investigates the Critical Success Factors (CSFs) for successful adoption and implementation of Green Information System (Green IS) in organizations. Extensive literature review conducted to identify the CSFs and these CSFs are validated through case studies of two Indian banks- State Banks of India (SBI) and Housing Development Finance Corporation Limited (HDFC). Nineteen CSFs are identified, namely: Leaders Obligation, Environment Changes, Industry’s Vision and Strategy, Resource Allocation, Expert Selection, Communication, Conflicts Resolution, Standard Adoption, Human Resource Induction and Training, Efficient Organization Structure, Cost-Benefit Analysis, Inspection/Audits, Financial Support, Technological Advancement, Customer Demand, System Integration, Rivalry Pressure, Awareness, and Government Policies. An interrelationship among these nineteen CSFs is established and a model is developed for effective Green IS implementation. Interpretive Structural Modeling (ISM) used to develop the model with the opinion of IT Experts and academicians. Moreover, this paper explores sustainability issues of Green initiatives. This study will enrich existing literature and assists researchers and policy makers in this area.