The 24-year-old won the Golden Boot in the Dutch top-flight before featuring in all three 2018 FIFA World Cup games for Iran has signed a five-year deal.
After scoring 21 goals and recording a further 12 assists in 33 games league games, Jahanbakhsh has made the switch to the Premier League, while reportedly rejecting the chance to join 2015/16 champions Leicester City.
"His versatility will increase our attacking options within the squad," said Brighton boss Chris Hughton about the winger who's comfortable on either flank and upfront.
His arrival marks the eighth major signing of the off-season including Tau, midfielder Yves Bissouma from Lille and Deportivo La Coruna striker Florin Andone.