The former Take That star will now perform at Hampden Park on Wednesday, June 26.
Tickets had already gone on sale for the initial date June 25. After being snapped up by huge demand in yesterday's pre-sale, another date was added.
He will promote his latest album Take The Crown, which simultaneously topped the charts alongside No 1 single Candy.
Earlier this year the singer played to 1500 fans at the Barrowland, but now he will play to more than 100,000 over the two nights.
Robbie, 38, said: "I have got such a buzz out of playing live again this year.
"The shows we have done have reminded me how special it is to play my songs in front of a huge audience, with all the excitement and adrenaline that it can bring."
Next year's shows will be his first full tour for more than six years and will take in 15 cities across Europe.
He recently became a dad after wife Ayda gave birth to daughter Theodora and he said they would be travelling with him on his tour.
He last visited Hampden in 2011 as part of Take That's Progress Live tour, which filled the 50-000 plus capacity venue for three successive nights.
Olly Murs will support Robbie as a special guest on all dates next year.
Olly said: "Everyone knows I am a huge fan of Robbie and I am honoured to call him my friend.
"He has been a huge inspiration to me and given me so much advice throughout my career.
"When he asked me to join him on tour I was delighted."
Tickets are now available from: www.tickets.robbiewilliams.com, www.ticketmaster.co.uk and www.ticketsoup.com