In a move that surprised media and political commentators, he will join the paper in May and edit it for "an average of four days a week", as well as continuing to fulfil his role as an MP.
Osborne said: "I am proud to be a Conservative MP, but as editor and leader of a team of dedicated and independent journalists, our only interest will be to give a voice to all Londoners.
"We will be fearless as a paper fighting for their interests. We will judge what the government, London’s politicians and the political parties do against this simple test: is it good for our readers and good for London? If it is, we’ll support them. If it isn’t we’ll be quick to say so."
The paper explained that Osborne will be able to edit the Standard in the morning and have time to vote and contribute to Parliament in the afternoon, and be in his constituency of Tatton.
Osborne said: "So much is now at stake about the future of our country and its capital city. I will remain in Parliament, where that future is debated. I was elected by my constituents in Tatton to serve them and I intend to fulfil that promise. I remain passionate about the Northern Powerhouse and will continue to promote that cause.
"Right from the first speech I gave about the North of England, I’ve said that London needs a successful north and the north benefits from its links to a global city like London. It’s not a zero-sum game, but quite the opposite," said the MP, who before the EU referendum had been tipped as a future prime minister.
Sands’ departure was announced in January. She is joining BBC Radio 4 to edit its flagship news programme, Today.