In 2003, he won the bronze medal in the 75 kg category at the 12th Senior World Boxing Championship in Bangkok, Thailand.[3] He lost to Andy Lee of Limerick, Ireland at the European Championships in Pula, Croatia on February 25, 2004.[4]
Nikola Sjekloća is a WBO International champion in the super middleweight division.
Sjekloća fought for interim WBC super middleweight title against Sakio Bika because of injured Andre Ward. However it was later changed and the fight was for number 1 contender that will fight for Andre Ward's World Boxing Council super middleweight title. Fight was promoted by Golden Boy Promotions and HBO and it was broadcast as one of the two main fights of the evening. It happened on February 16, 2013 in Boardwalk Hall, Atlantic City, New Jersey, USA. Sjekloća convincingly lost the fight by unanimous decision, and this fight was his first career loss.[5][6]
^"Nikola Sjekloca wins bronze". Serbian Government, Office of Media Relations. Serbia-Montenegro's Nikola Sjekloca won bronze medal at the 12th Senior World Boxing Championship in Bangkok, Thailand. 2003-07-11. Retrieved 2008-10-19. [dead link]