The Badshahi Mosque located within the Walled City was also visited by William's grandmother Queen Elizabeth II when she was in the country with husband Prince Philip in 1961, and his late mother Princess Diana during her 1991 tour, reports Dawn news.
During the visit on Thursday, the Duke and Duchess of Cambridge changed into formal attire with William sporting a suit and tie and Middleton donned a green tunic, trousers and dupatta.
Following their trip to the mosque, the couple paid a visit to the Shaukat Khanum Memorial Cancer Hospital and Research Centre, where they met children suffering from cancer and also visited the department hosting the hospital's radiation machine.
Princess Diana, who was a friend of Prime Minister Imran Khan, visited Pakistan twice - 1996 and 1997 - to help raise awareness and funds for the Shaukat Khanum Memorial Cancer Hospital.
In the evening, the Royal Air Force plane carrying the royal couple was forced to abort a landing in Islamabad twice and return to Lahore after being caught in a severe thunderstorm.
The couple - who are the first British royals to officially visit Pakistan since Prince Charles and his wife Camilla visited the region in 2006 - were received by Punjab Chief Minister Usman Buzdar and Governor Chaudhry Sarwar upon arrival at the Lahore airport on Thursday morning.
The Duke and Duchess arrived in Islamabad for their maiden visit to Pakistan on Monday night.
They will return to the UK on Friday.
( With inputs from IANS )