The oath of office was administered by President Asif Ali Zardari, reported Geo TV.
Sharif became the first third time prime minister in the history of the country after he secured 244 votes with his rivals Pakistan Peoples Party's Makhdoom Amin Fahim and Pakistan Tehreek-i-Insaf's Javed Hashmi bagging 42 and 31 votes, respectively.
Former prime ministers Yousuf Raza Gilani and Raja Pervez Ashraf attended the oath taking ceremony. Army chief General Ashfaq Parvez Kayani too was present.