Mrs Merkel urged her party to celebrate "a super result" as she looked set for a historic third term.
Her conservative bloc took about 41.5% of the vote - but her liberal partners failed to make it into parliament.
It is thought she is likely to seek a grand coalition with the Social Democrats (SPD) who won 26%.
This is an amazing result for Angela Merkel, currently Germany's - and Europe's - pre-eminent politician. It was clear that she would win this election, but no-one really predicted that she could get so close to an absolute majority.
The final results are not yet in, but it may still be that she needs a coalition partner. The obvious solution is a grand coalition with the centre-left Social Democrats. The party improved its share of the vote in second place, but still did not do as well as it wanted.
But there are divisions within the SPD about going into coalition again as a junior partner. In 2009 they were punished by the electorate for doing that in 2005.
Now the same thing has happened to the liberal Free Democrats, who have been in coalition with Mrs Merkel for the last four years, but appear to have been kicked out of parliament altogether.
The results showed that the liberal Free Democrats (FDP) won only 4.8%, which correspondents say is a disaster for the junior coalition partner, leaving it with no national representation in parliament for the first time in Germany's post-war history.
Party chairman Philipp Roesler called it "the bitterest, saddest hour of the Free Democratic Party".
The FDP was beaten by the Green Party (8.4%) and the former communist Left Party (8.6%). It almost finished behind the new Alternative fuer Deutschland (AfD), which advocates withdrawal from the euro currency and took 4.7%, just short of the parliamentary threshold.
There was at one point speculation that Mrs Merkel's Christian Democrats (CDU) and their Bavarian sister CSU might even win enough seats for an absolute majority - the first in half a century.
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Final percentage of the vote
CDU bloc: 41.5%
Left Party: 8.6%
Mrs Merkel earlier addressed jubilant supporters at CDU headquarters. After waiting for chants of "Angie, Angie" to die down, she told them: "This is a super result."
"We can celebrate tonight because we have done something fantastic."
But, in a reference to coalition building, she said it was "too early to say exactly what we'll do".
Correspondents say that the 59-year-old chancellor seemed to acknowledge the complexities of forming a government when she was asked on television if she planned to reach out to other parties.
"Maybe we won't find anyone who wants to do anything with us," she replied.
Correspondents say that the result is nevertheless a ringing endorsement of her steady leadership during the euro zone crisis.
Mrs Merkel has made clear she would be prepared to work with the Social Democrats (SPD) in a grand coalition, as she did in 2005-09.
The SPD has been more reluctant to consider linking up with the CDU/CSU again. The party leader, Peer Steinbrueck, was finance minister in the previous grand coalition, but has said he would not serve in such a government again.
Correspondents say that whatever the shape of the coalition that ends up forming the government, there probably will not be any significant policy shifts, although Germany might take a slightly softer approach to austerity in the eurozone.
Several weeks of difficult coalition negotiations are expected.
Peer Steinbrueck: "We did not get the result we wanted"
After the exit polls were released, but before official results were confirmed, Mr Steinbrueck conceded that it would be up to Mrs Merkel to decide how to proceed saying: "The ball is in Mrs Merkel's court. She has to get herself a majority."
The BBC's Chris Morris, at Social Democrat headquarters, said Mr Steinbrueck was putting a brave face on it but the atmosphere was subdued.
The SPD would have preferred to enter a coalition with the Green Party, but does not appear to have the votes to do so, and has ruled out a three-way alliance including the Left Party (Die Linke).
Analysts think the SPD will probably agree to a coalition with the CDU/CSU.
Turnout, projected at about 72%, was higher than at the last federal election - which had the worst on record.