Stores in and around Buchanan Street, Sauchiehall Street and Argyle Street will open until 8pm during the week until August 3.
The move comes nine months after Style Mile retailers opted to keep their doors open until 7pm.
Shopping bosses say that decision has led to increased footfall and a "culture change" that keeps people in the city centre later.
More than five million people visited the city centre in May this year - the best month for footfall since records began four years ago.
Retail chiefs now want to take advantage of the Commonwealth Games and other summer events by keeping shops open longer.
Among the malls and shops staying open until 8pm are the St Enoch Centre, Buchanan Galleries, House of Fraser, Argyll Arcade and Forever 21.
Anne Ledgerwood, chairwoman of the City Centre Retail Association and manager of the St Enoch Centre, said: "When we began staying open until 7pm it was quite a culture change but it really has been a success.
"Tourists expect the city centre to be open - and we need to show that we're open for business."
Ann Smith, 22, from Royston, said: "People would usually go out to Braehead or the other out of town centres for late-night shopping so it's handy to have it in town."