The design and development of novel, metal-free heterogeneous catalyst for organic transformation reactions is a challenging task. Amine functionalized graphitic carbon nitride (NH2-GCN) was prepared and used as a heterogeneous base catalyst for Knoevenagel condensation reaction. The amine functionalization leads to increased basicity due to the presence of additional -NH2 groups. The catalytic potential of NH2-GCN was tested for Knoevenagel condensation, which showed a good catalytic activity. The detailed optimizations of various reaction conditions such as, time, temperature, and catalyst amount were performed. All the reactions were performed under optimal conditions, as determined. Catalyst showed highest yield of 92% and only single product is formed. It also exhibits high turnover number. In addition to that, green metrics calculations were determined. To check the heterogeneous nature of the catalyst, recyclability studies were also performed. This catalyst provides a green, sustainable, and metal-free approach for Knoevenagel condensation reaction.