Temperature and rainfall are the major climate factors affecting crop growth and development, especially under rain-fed agriculture. The changing and diversified climatic conditions of Khyber Pakhtunkhwa (KPK) from northern to southern regions under the current climate change scenario, may pose serious threat to crop production and livelihood. Addressing these issues and keeping in view the importance of wheat as a major staple crop of Khyber Pakhtunkhwa (KPK), this research study was conducted to assess the impact of climate change on net irrigation requirement (NIR), actual crop evapotranspiration (ETc) and reference crop evapotranspiration (ETo) of wheat crop using Penman Montieth method through CROPWAT model developed by Food and Agriculture Organization (FAO), while using historical weather data from 1961-2010 of Dera Ismail Khan. The results showed increasing temporal tendency in temperature and rainfall during the study period. Positive correlation was found between temperature and ETo, ETc and NIR, which indicate increasing tendency in water demand in future, thus may lead to negative consequences for crop growth and development, if appropriate measures were not undertaken timely. In contrast, rainfall showed negative correlation with ETo, ETc and NIR, which may support in meeting crop water demand in future, thus may boost wheat production. Importantly, the increasing temporal tendency of rainfall and temperature necessitate the need for greater rainwater harvesting to meet the increasing irrigation requirement in Dera Ismail Khan Division.