We report the observation of an emerging Mott-insulating barrier at the interface between epitaxial c-axis oriented superconductors Pr1.85Ce0.15CuO4 and La1.85Sr0.15CuO4 thin films. Atomically sharp bilayers were grown via pulsed laser deposition. The quality of the interface was inferred from X-ray diffraction and scanning transmission electron microscopy. Electrical transport measurements were carried out to reveal, from unusual signatures, the existence of an emergent insulating barrier at the interface between the two layers. A simple model including a resistive interface separating two superconducting layers was constructed to reproduce the unusual signatures and to extract the large resistivity of the interface. The insulating nature of the barrier was later confirmed from nonlinear characteristic transport through the interface. The absolute value of the measured resistance finally suggests that the barrier is a Mott insulator which is compatible with a charge transfer between the two layers.