Janković's term as mayor ended after the 4 December general election, which was won by his Positive Slovenia. He tried to set up a coalition, but failed to get majority support in the National Assembly.
His return to the city hall was not a surprise, as he had made it clear from the beginning that he was only interested in becoming prime minister.
Janković said at today's inauguration that the trust demonstrated by the people of Ljubljana once again showed that his work in the past five years was to the benefit of all.
"I was in parliament for good three months and it has been a very good lesson for me. I have to say that our discussions here at the city council are much more productive, much more tolerant." He said he was very happy to return to the great "family of the city, the best team" that includes 12,000 people.
In his speech, Janković also touched on topical issues in national politics, expressing disagreement with the government's plan to cut public sector pay by 13%.
He pointed to an agreement between most parties and the trade unions signed in January under which the public sector pay would go down only 2% annually.
He also pointed out that the government-proposed austerity measures will affect local communities, as funds for municipalities will also be reduced.
Janković moreover called upon public sector trade unions to postpone the general strike planned for 18 April for a month to give the National Assembly a chance to pass the 2012 supplementary budget. He added that strikes and referendums were doing "damage to the country, which we all will have to pay for".
A law adopted in May last year made the mayoral post incompatible with the post of deputy at the National Assembly. A mayor standing for MP loses office as soon as he or she is elected.