This paper is devoted to the study of head-on collision between a couple of dust-ion acoustic solitary (DIAS) waves in an unmagnetized dusty plasma comprised of inertial ions, negatively charged stationary dust grains and nonextensive electrons. To this end, using the extended Poincaré–Lighthill–Kuo approach, two Kortwege–de Vries equations for solitary waves are derived and the analytical phase shifts after the head-on collision of two DIAS waves are obtained. In the following, based on the numerical calculations the effects of the relative density and nonextensivity on phase shifts are investigated. The results show that the presence of nonextensive electrons in dusty plasma has noticeable effect on the characteristics of DIAS waves' collision. We believe that these results can be of usable in getting more insight into the DIAS waves' collision in laboratory and astrophysical plasmas.