At the age of 17, he emigrated with his parents to the USA.[6] In 1987, he received a Bachelor of Arts degree from the University of St. Thomas in Houston, and in 1990 a Juris Doctor degree from Harvard Law School.[4] From 1990 to 1997, he served as a partner with White & Case and Vinson & Elkins in New York, Houston and Warsaw.[4] He then served as a partner at CMS Cameron McKenna in London until 2007.[4] In the years 2007–2013 he was the president of the Kulczyk Investments group.[6]
In July 2012, he joined the supervisory board of Legia Warsaw football club. Five months later, Bogusław Leśnodorski became the club's president. In January 2014, he and Leśnodorski became the owners of Legia Warsaw, buying 100 per cent of the company's shares from the ITI Group.[6] Mioduski became the majority shareholder (80 percent). In time, 20 per cent from Mioduski was taken over by Maciej Wandzel.[7] On 22 March 2017, he purchased the remaining forty percent of the club to become the single owner of the club from Bogusław Leśnodorski.[8]
In 2015, he was awarded the Gold Cross of Merit by President of Poland Bronisław Komorowski.[9]
On the night of 5-6 October 2023, after the end of the Europa Conference League match between AZ Alkmaar and Legia Warsaw, there was a clash between Legia players and staff on one side, and AZ Alkmaar security and Dutch police on the other.[10] A video was published online showing Dariusz Mioduski being pushed and beaten by Dutch police.[10] As a result of the incident, two Legia players Josué Pesqueira and Radovan Pankov were arrested.[10] They were released the next day, Josué was not charged.[11] During a press conference on 6 October, Dariusz Mioduski called the incidents in the Netherlands "an absolute scandal," accused the Dutch media of propagating an untrue narrative and announced efforts to clarify the entire situation.[12] On 15 December, UEFA charged AZ with a €40,000 fine for failing to provide security for the Polish side at the AZ Stadium.[13]
