His new job will be much more daunting -- he inherits a nation riven with economic woes, security threats and a resurgent military looking to increase its grasp on political life.
It's a lot for a politician who has enjoyed a rapid rise but whose party has, until now, struggled to make an impact on the national level.
Running a populist campaign directed at the nation's disenchanted middle class, Khan has drawn comparisons with another upstart celebrity-turned-politician: US President Donald Trump.
"He sounds like Trump -- what Trump is for the US, Khan will be for Pakistan," said Ayesha Siddiqa, analyst and research associate at London's School of Oriental and African Studies (SOAS) South Asia Institute.
Much like his US counterpart, Khan's celebrity has facilitated his rise. He has "several faces, as a sportsman and a hero," said journalist Zahid Hussain. "It's one of the reasons for his popularity, his charisma."
"He's a contradiction -- he's supposed to be a modern face but (has) lots of conservative thinking, on Taliban, religious issues," said Hussain.
The Election Commission of Pakistan announced on Saturday that Khan's PTI had won 115 of the 270 available seats, giving it a minority win in parliament. Analysts say, however, that he will have no problem forming an alliance to rule the nation as prime minister.
In claiming victory on Thursday, Khan put his religion on show, saying that "God has taken me to that level, given me an opportunity of a dream."
"God has given me that chance to fulfill that dream."
Dealing with Trump
Regardless of whether Khan becomes the Donald Trump of Pakistan, he will be expected to engage with the US leader, having distinguished himself as a candidate as a harsh critic of Washington, long Pakistan's most important military ally. But analysts have expressed skepticism over whether he will be willing to actually take on Washington.
Khan was an outspoken opponent of drone strikes in Pakistan's tribal areas, and called for the country to be less economically reliant on the US, but is likely to tone "down some of the rhetoric," said Siddiqa, the SOAS expert.
In a speech delivered Thursday night, he said that he is looking for "mutually beneficial relations" with the US.
"At the moment we have a one-way relationship with the US," he said. "America is fighting its own war. We need a balanced relationship with the United States."