Adjaye was awarded the biggest of the four prizes, the Panerai London Design Medal.
The Tanzanian-born British architect was described by judges "an inspiration for the younger generation".
His projects include the Dirty House in London's Hackney and the Sugar Hill housing block in New York, as well as the new Smithsonian Museum of African American History and Culture.
Adjaye becomes the 10th winner of the prize, which has been awarded annually since 2007 to an individual or group that has demonstrated "an outstanding contribution to London and design".
Kenneth Grange was given the Johnson Tiles Lifetime Achievement Medal to acknowledge his significant influence on the design industry, as founder of Pentagram, and for products like the InterCity 125 train and the first UK parking meter.
Judges described Grange as "the godfather of UK product design".
"Every household in the UK must have a product designed by him – his designs truly are icons that will feature in the history books," they said.
The awards programme also presented medals for design innovation and emerging talent. The Swarovski Emerging Talent Medal was awarded to Bethan Laura Wood, who is known for her colourful approach to ceramics and installations.
The Airbnb Design Innovation Medal went to Rotterdam-based designer Daan Roosegaarde, whose studio has launched a series of environmentally conscious projects ranging from a "smog vacuum cleaner" to glow-in-the-dark trees.
Work by the four winners will be presented within a pavilion in Exchange Square at Broadgate, as well as in an exhibition in the Shoreditch Design Triangle district.
The London Design Festival officially opened to the public at the weekend, and continues until 25 September 2016. Highlights include a kinetic installation at the V&A, an inhabitable wooden "mega-tube" and a series of huge transparent boxes filled with plants.