The 49-year-old was one of Germany's pioneering players within the PDC, and alongside Andree Welge became the first German competitors in the World Darts Championship in the 2005/06 event.
Seyler defeated Jamie Harvey before losing to Roland Scholten at the Circus Tavern on his World Championship debut, which sparked the sport's growth in his homeland.
He would make three further World Championship appearances, and also qualified for a trio of European Championships and the 2013 UK Open.
Nicknamed "Shorty", Seyler last competed on the PDC circuit in 2016, but remained active in Germany and also moved into commentary with broadcasters Sport1 and DAZN.
A three-time German National Champion, Seyler had been admitted to hospital on June 29, and passed away on July 11.
In a statement, Seyler's daughter Tara and fiancé Wiebke said: "Shorty has always met life with humor and charm and has inspired us all with his passion for darts."
Sport1 editor-in-chief Michael Langkau said: "Shorty lived for darts - and did pioneering world as an expert with his very own emotional manner.
"Thanks in part to his great commitment and enthusiasm for darts, which has been transferred to his audience, the sport now also captivates millions of spectators in Germany.
"Beyond his [commentary] work, we will remember Shorty above all as a wonderful person and great guy."