The photodegradation of a new family of thermoplastic elastomers, based on blends of natural rubber and polyethylene, was studied with laboratory ultraviolet exposures in the unstrained state and under tensile strain (25 and 50%). Strained exposure caused reduction of the strain to failure in subsequent tensile tests. The blends were more resistant to degradation than the natural rubber homopolymer. The introduction of crosslinks (at a low concentration so that the thermoplastic nature of the blends was retained) changed the resistance to photo-oxidation. Two different crosslinking systems were used. When dicumyl peroxide was used as the crosslinking agent, the resistance to degradation was reduced, whereas the compound containing a sulfur curing system showed improved resistance to photodegradation. Photo-oxidation rather than ozone degradation was found to be the major cause of breakdown, even with samples held in tension.