A general, mild, efficient and practical approach for the construction of functionalized γ-carboline derivatives has been successfully realized in water through a one-pot three-component reaction involving several aryl/hetero-aryl/alkyl/alkenyl/alkynyl/ferrocenyl aldehydes, 3-formyl indole derivatives and ammonium acetate as a cheap N-source. The most important feature of the current methodology is that this hetero-annulation reaction of indole to γ-carboline can occur in good to excellent yields with wider substrate scope at room temperature in water, starting from simple inexpensive raw materials under catalyst-free and oxidant-free conditions. Moreover, a facile access to pentacyclic quinolinone fused carboline derivative has been achieved through our methodology.