David Cameron’s title is to be Lord Cameron of Chipping Norton.
The former Prime Minister is due to be introduced to the Upper Chamber on Monday.
He will then lead a debate on a trade bill on Tuesday.
His appointment, while welcomed by a number of Tory MPs, has proved controversial partly because he will not be able to be questioned in the Commons.
Foreign Office minister Andrew Mitchell will take questions in the Commons instead.
Such arrangements are not unprecedented, with Labour’s Lord Mandelson having been Business Secretary, but they are unusual.
Lord Cameron was MP for Witney before he stood down in 2016 after losing the Brexit referendum.
He was said to be part of the “Chipping Norton set”, named after the Oxfordshire village where a number of prominent individuals live, or have homes close by, including former Top Gear presenter Jeremy Clarkson and Rebekah Brooks, head of the British media organisation created by Rupert Murdoch, News UK.
Lord Cameron was made Foreign Secretary in Rishi Sunak’s reshuffle on Monday which saw Suella Braverman sacked as Home Secretary.
She was replaced by James Cleverly who moved from the Foreign Office.
Lord Cameron visited Kyiv this week where he held talks with Ukraine’s president Volodymyr Zelensky and also travelled to the Black Sea port of Odesa.
In Ukraine's capital, the Foreign Secretary stressed: "What I want to say by being here is that we will continue to give you the moral support, the diplomatic support... but above all the military support that you need not just this year and next year, but however long it takes."
He added that Britain would work with its allies "to make sure the attention is here in Ukraine," given the focus also on the Israel-Gaza conflict.
Lord Cameron visited Moldova after his trip to Ukraine and discussed security in the Black Sea and bilateral cooperation with Moldovan President Maia Sandu.
"Expressed gratitude for the UK's support to Ukraine: crucial for Moldova's security and the stability and prosperity of Europe," Ms Sandu said on X, formerly known as Twitter.
Pro-European Ms Sandu has denounced Russia's invasion of Ukraine, accused Moscow of plotting to oust her and thrown her weight behind a drive for Moldova, an ex-Soviet state, to secure European Union membership.
During her meeting with Cameron, the two also discussed "united stance against corruption", she said.
