Career
Kolev started to play football at Etar Veliko Tarnovo. Kolev made his competitive debut for Levski on 27 October 1999 against Football Club Iskar in the first round of the Bulgarian Cup, scoring three goals. In June 2000, he was loaned to Spartak Pleven.
In the 2001-2002 season, Kolev earned 23 appearances playing in the Bulgarian top division, scoring 18 goals.
In January 2005, Kolev was loaned to Marek Dupnitsa. Five months later, Slavia Sofia signed Kolev on a five-year deal.
In the 2006-2007 season, he scored the 25 goals in 28 league matches. In June 2007, Kolev relocated to Germany, signing a contract with Turn- und Sportverein Alemannia Aachen.
In the 2007-2008 season, he earned 20 appearances playing in the 2nd Bundesliga, scoring five goals.
In August 2008, Kolev returned to Slavia Sofia. In December 2010, Kolev signed with Ludogorets Razgrad. In September 2012, Kolev left Etar 1924 to sign with Olympiakos Volou.