Laser induced photo-thermal resistance response (PTRR) of polyisoprene/nanographite (PN) composites was studied. An inverse character of photoresistance in comparison to semiconductor-like materials was observed: electrical resistance of the PN composite increases when the intensity of the laser radiation is increased. The observed response can be explained by the photo-thermal effect: if the temperature of the PN composite rises because of optical radiation absorption then the electrical resistance increases due to positive temperature coefficient of the composite. Theoretical explanation of the positive temperature coefficient effect in PN composites based on tunneling-percolation model is given. © 2016 Elsevier Ltd. All rights reserved.