Greece qualified for a second successive World Cup after another Kostas Mitroglou goal secured a 1-1 draw with Romania in the second leg of their playoff on Tuesday, and a 4-2 victory on aggregate.
Mitroglou, who scored twice in Greece's 3-1 first-leg win on Friday, beat the offside trap midway through the first half and gave keeper Ciprian Tatarusanu no chance with his 22nd goal in all competitions this season.
Romania equalised 10 minutes after the break when Vasilis Torosidis struck the ball past his own goalkeeper, Orestis Karnezis, from the edge of the area for an astonishing own goal.
Greece, the 2004 European champions, competed in the previous World Cup finals, in South Africa in 2010, as well as the 1994 tournament in the United States, but they have failed to get past the first round, losing five of their six matches.
The Greeks arrived in Bucharest after seven consecutive wins aiming to produce another solid defensive display, with Bogdan Stancu's strike at the Georgios Karaiskakis Stadium on Friday ending their run of 594 minutes without conceding a goal.
Greece coach Fernando Santos made only one change from the team that humbled the Romanians in the first leg, with 36-year-old veteran Giorgos Karagounis replacing suspended captain Kostas Katsouranis in midfield in his 131st international appearance.
The home side, who have failed to reach the World Cup finals since 1998, dominated the early stages with winger Gabriel Torje continually tormenting the Greece defence on the right flank but were unable to create any clear-cut chances.
It was Greece who almost broke the deadlock after 17 minutes - in their first attack of the game - when Ciprian Tatarusanu produced a brilliant save to deny Jose Holebas's fierce left-foot effort.
Tatarusanu and centre back Vlad Chiriches returned to Victor Piturca's starting lineup after recovering from injuries while midfielders Ovidiu Hoban and Alexandru Maxim replaced Alexandru Borceanu and Razvan Cocis.
More than 50,000 Romanian fans created an intimidating atmosphere for the visiting players but Piturca's side looked bereft of ideas, and strikers Ciprian Marica and Stancu struggled against the well-organised visitors.
Greece, who went into the playoffs after finishing behind European qualifying Group G winners Bosnia on goal difference, held their nerve after their bizarre own goal.
Romania's failure - they were also knocked out of another World Cup playoff in 2001, to Slovenia - is the latest setback for Piturca, as the 57-year-old was also in charge of the Romanian teams that missed the 2006 and 2010 finals.