Mr Khan unofficially confirmed his victory yesterday with a statement recorded at his house.
He has promised a new Pakistan after an election that was marred by violence and allegations of vote rigging.
Khan’s Pakistan Tehreek-e-Insaf (PTI) party won 109 of the 269 seats being contested in the National Assembly.
Any one party needs 137 votes to win an overall majority.
The closest rival, Shahbaz Sharif’s Pakistan Muslim League won 63 seats.
Third place went to the left of centre Pakistan People’s Party with 39 seats.
There are a total of 20 results still to be announced.
During his victory speech on Thursday, Imran Khan promised a welfare state system based on the British model.
He also pledged to “strengthen institutions” and “increase income” in order to “get more taxes and benefit the country”.
He said: “This election is a historic election in Pakistan. In this election, people have sacrificed a lot.
“There was terrorism in this election. I want to especially praise the people of Balochistan, the kind of difficulties that they had to face.
“The way they came out to vote, I want to thank all those people.”
He said the election had been the fairest in the country’s history: “I feel that this election has been the fairest in Pakistan’s history.
“If any party has any doubts, we will open the results of those constituencies up for investigation.”
On Thursday, opposition leader Shahbaz Sharif pledged to challenge the eventual election result amid allegations of vote rigging.
There were said to be problems in the ballot process such as electoral observers not being allowed into polling stations and voters not being given appropriate forms on time.
An official announcement is expected on Friday after the last 20 votes have declared.