Members of the new assembly sworn in and plan to elect the speaker and deputy speaker of the house. Imran Khan, former cricket star and leader of Pakistan Tehreek-e-Insaf, says it enjoys the backing of 180 lawmakers in the 342-seat assembly.
Pakistan's newly-elected parliament has met for the first time since last month's general elections.
The lawmakers were sworn in at a brief ceremony in the house on Monday, after which they are to elect a parliament speaker and deputy speaker.
The National Assembly will also vote on the new prime minister, who will be sworn in on August 18. Later on Monday, fireworks are to mark the eve of Pakistan's Independence Day.
Pakistan Tehreek-e-Insaf, the party of Pakistan's cricket star-turned-politician Imran Khan, says it enjoys the backing of 180 lawmakers in the 342-seat assembly.
Khan needs 172 votes to become prime minister.
Khan has campaigned on the promise of a "New Pakistan" with justice for all, pledging to wipe out corruption and help the poor.
He has said he would run the country like it has never been run before, though some of his popular and influential backers, who joined his party weeks before the elections, have questionable pasts and some of them even face charges.
The 65-year-old has also promised to create 10 million jobs in Pakistan, where the employment rate is high and more than 65 percent of the country's 200 million people are under the age of 35.
Since the elections, Khan has adopted a conciliatory approach to Pakistan's neighbours and allies, saying he wants peace with hostile neighbour India, praising China's economic strategy for reducing widespread poverty and sending a message to Washington that he wants good relations, based on mutual respect.
He also reached out to Afghanistan, suggesting the two nations adopt a policy of open borders, a relationship similar to the European Union. Khan has also disparaged liberals, attacked feminism, embraced radical religious parties like others have before him and vowed to uphold Pakistan's blasphemy law.
He enjoys the support of the country's powerful military establishment, although he has been known to go his own way.
Claims of rigging in elections
Pakistan Peoples Party chairman Bilawal Bhutto-Zardari, former president Asif Ali Zardari and head of the ex-governing Pakistan Muslim League-Nawaz (PML-N) party Shehbaz Sharif were also at the ceremony.
All provincial assemblies also took oath on Monday, with the exception of Punjab, Dawn.com reported. Khan and Sharif are expected to face-off for the prime minister's spot, the English-language news organisation said.
The PML-N has claimed the elections were rigged to prevent disgraced former prime minister Nawaz Sharif from returning to power.
Nawaz, who is currently appealing a 10-month prison sentence for the misuse of funds to purchase luxury apartments in Britain, was arrested on July 13 after returning from London.
As Pakistan's new lawmakers took their oath of office, Nawaz was taken by armoured car from his jail cell at Adiala prison to the accountability court in the capital, Islamabad, to face more corruption charges.
Nawaz's daughter Maryam was sentenced to seven years in the same case and her husband to one year.