LDA Design has been chosen to breathe new life into Union Terrace Gardens.
Four years ago, councillors rejected plans for a Â£140m transformation of the gardens. Businessman Sir Ian Wood had offered Â£50m towards the cost.
A city centre masterplan, agreed by councillors last year, will be used as a blueprint by the designers.
It suggests that the gardens could be used to stage year-round events and historic arches could house shops, cafes and artists' studios.
It also outlines plans to improve access by providing lifts, ramps and new stairs.
LDA Design said the gardens could have an activity area for children, a horticultural hotspot, a cultural hub, and open air exhibitions and performances.
Project director Kirstin Taylor said: "The city centre masterplan provides a powerful vision to set Aberdeen apart on the global stage and the gardens have a huge part to play.
"The masterplan attracted lots of positive local engagement which we want to harness. We see the community's ongoing participation as key to the gardens' success.
"Union Terrace Gardens have great beauty and charm, and can be revitalised in a way that completely respects and enhances their 19th century heritage.
"They can offer traditional park enjoyment alongside new ideas and uses, and LDA Design is experienced in securing this kind of careful balance."
The design team behind London's Olympic Park has been been given the task of drawing up detailed plans to regenerate an historic Aberdeen city centre park.