We study, through path-integral methods, an extension of the massive Thirring model in which the interaction between currents is non-local. By examining the mass expansion of the partition function we show that this non-local massive Thirring model is equivalent to a certain non-local extension of the sine-Gordon theory. Thus, we establish a non-local generalization of the well known Coleman's equivalence. We also discuss some possible applications of this result in the context of one-dimensional strongly correlated systems and finite-size quantum field theories.Facultad de Ciencias Exactas