Steven Lamar claimed credit for the idea of creating a brand of celebrity-endorsed headphones.
He took the idea to Dre and Iovine in 2006; and the first Beats headphones were released two years later, based on a design by Robert Brunner.
The parties later fell out, and Lamar sued over unpaid royalties in 2016.
At the centre of their dispute was a 2007 settlement, in which Dre and Iovine agreed to pay Lamar 4% of the base price of every headphone they sold.
Only one model, Beats Studio, was specified but Lamar argued the design had been carried over to a dozen different models, and sought $130m (£99m) in royalties.
A jury in Los Angeles decided that three pairs of headphones – the Studio 2 Remastered, the Studio 2 Wireless and the Studio 3 – had design similarities; and ordered that Dre and Iovine should pay Lamar $25,247,350.
With the Studio 3 still on sale, the verdict means Lamar will continue to receive royalties in addition to the court-mandated payout.
For more details: bbc.com