Poly(propylene) (PP) films containing different concentrations of bis(benzoxazolyl)stilbene (BBS) have been prepared by melt processing. We demonstrate that the emission characteristics of PP films depend on BBS concentration and polymer deformation. A well-defined excimer band is observed with more than 0.2 wt.-% of BBS, conferring to the film a green luminescence. During drawing (130 degrees C) the PP reorganisation breaks the BBS excimer-type arrangement, leading to the prevalence of the blue emission of the single molecules. We have efficiently applied the photophysics of this commercial stilbene derivative to the production of powerful tools acting as an internal probe for PP deformation.