The post has been lying vacant since May, when the then envoy, Pakistan People's Party leader Sherry Rehman, resigned after the PML-N swept to power in the general election.
The government had decided last month to make Jilani, who served as Deputy High Commissioner to New Delhi during 1999-2003, the new envoy to the US.
A statement from the Foreign Office said Jilani "will join his new assignment in December".
Senior diplomat Abdul Basit will replace Jilani as the Foreign Secretary, officials said.
Born on February 2, 1955, Jilani has a Bachelor's Degree in Law and a MSc in Defence and Strategic Studies.
In his career, he has specialised in South Asian affairs and served in the Foreign Office as Director India during 1992-95 and Director General South Asia and SAARC during 2003-07. In 2005, he served as the Foreign Office spokesman.