The head-on collision of dust acoustic solitary waves in a three-component unmagnetized dusty plasma with Boltzmann distributed electrons, nonthermal ions and negatively charged dust grains has been investigated using the extended Poincare-Lighthill-Kuo method. The effects of the ratio of electron temperature to ion temperature on the phase shift have also been studied. It is found that the presence of nonthermal ions play a significant role on the collision of dust acoustic solitary waves. There are real implementation of present results in different regions of space, viz cometary tails, upper and lower mesosphere, Jupiter’s magnetosphere, etc.