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.
"We have seen lots more office workers taking advantage of the extended opening hours.
"We've also seen a rise in tourists in the city shopping later.
"Tourists expect the city centre to be open - and we need to show that we're open for business.
"Historically, people would come into town, shop and then go home before coming in to party.
"But now people stay right through because the city centre doesn't shut."
Store managers are feeling positive about the shift in trading hours.
Footfall at Buchanan Galleries was up every week in January and February this year, by as much as 40%.
Meanwhile, the St Enoch Centre now sees nearly 20% of its weekly footfall between 5pm and 7pm.
They also found the Easter school holidays were busy between 5pm and 6pm, with an increase in shoppers of around 20% on 2013.
It is hoped that the initiative will boost the high street.
Ms Ledgerwood said: "Glasgow is the second best retail destination in the UK after London, we need to sustain that and adapt to what our customers needs and wants are."
Shoppers welcomed the move.
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."
Vikki Ellis, 32, an after school club manager from the city centre, said: "Having the shops open after work is really useful - it means you can get things done during the week."