His swearing in ceremony marks the end of decades of rotating leadership between two establishment parties, accompanied by periods of military rule.
The 65-year-old, wearing a traditional black sherwani and black glasses, shed a tear and smiled as he stumbled over some of the words of the oath.
He was accompanied by his third wife, Bushra Bibi, formerly known as Bushra Maneka, who he wed earlier this year.
It was her first public appearance since the wedding, and wearing a traditional white niqab she was flanked by tight security.
The swearing-in ceremony came a day after Oxford graduate Mr Khan won a simple majority from MPs, three weeks after the 25 July general election.
After winning the confidence vote he promised a new era of responsibility and prosperity in a powerful speech, saying he would combat Pakistan's endemic corruption and break powerful landowners' monopoly on political power.
Branded "Pakistan's dirtiest" election, the military was accused during the campaign of attempting to influence people to vote for Mr Khan.
Since last month's election opposition parties have held regular protests.
The army and Mr Khan have denied claims from opposition parties of "blatant" vote rigging.
Mr Khan and his Pakistan Tehreek-e-Insaf (PTI) party fell short of an outright majority, forcing him to partner with smaller parties and independents to form a government.
The former cricketer has been on a long road to lead the country, forming his party in 1996 - four years after he led Pakistan to World Cup victory in 1992 - with a vow to create a corruption-free "new Pakistan" with justice for all.
Over the past two decades he has challenged the parties of three-time prime minister Nawaz Sharif and former president Asif Ali Zardari.
His efforts were not rewarded until 2013 when his party become the third-largest in the parliament's lower house.
Source : Afghan Voice Agency(AVA)
Saturday 18 August 2018 10:35