Due to their rather low efficiencies in solid films, successful applications of conjugated polymers are scarce. However, recently several experiments indicated that a proper control of molecular conformations and stresses acting on the polymers may provide constructive ways to boost efficiency. Here, we report an amazingly large enhancement of photoluminescence as a consequence of strong shear forces acting on the polymer chains during nanofilm dewetting. Such sheared chains exhibited an emission probability many times higher than the non-sheared chains within a non-dewetted film. This increase in emission probability was accompanied by the emergence of an additional blue-shifted emission peak suggesting reductions in conjugation length induced by the dewetting-driven mass redistribution. Intriguingly, exciton quenching on narrow-bandgap substrates was also reduced, indicating suppression of vibronic interactions of exciton. Dewetting and related shearing processes resulting in enhanced photoluminescence efficiency are compatible with existing fabrication methods of polymer-based diodes and solar cells.