An AcOH-mediated concise, atom-economical and environmentally sustainable tandem strategy has been formulated to access highly fluorescent (Φ_F up to 40%) N-fused bis-carbolines, imidazopyrido[3,4-b]indoles and imidazo[1,5-a]pyridines via the formation of three C–N bonds in a single operation. The multicomponent character of the reaction, easy to execute reaction conditions, simple purification procedure and excellent light emitting properties of the product afforded thereof provide a huge scope.