In February 2007, he played for the Australian Under-23 team, the Olyroos, in an Olympic qualifier in Adelaide, scoring the 11th goal in Australia's 11–0 win over Chinese Taipei.
Raul Blanco played him in a striking role alongside Mark Viduka in all of Australia's matches against Italy, Nigeria and Honduras, but he did not score as the Olyroos failed to progress beyond the group phase.
Nikolai is the most capped Olyroos player representing Australia at the 2008 Beijing Olympic Games.
After having an injury ravaged 2006/7 season, Dilevski was a member of the Olyroos Squad (under the tutelage of Rob Baan) in preparation for the 2008 Beijing Olympics, but eventually missed out on a place in the final squad for the tournament.