The administration of George Bush, the previous US president, had boycotted the council over its criticism of Israel and its failure to cite rights abuses in Sudan and elsewhere.
In March, the Obama administration said it would seek to join the council as part of a "new era of engagement" with the body.
Set up by in 2006 by the UN General Assembly to address incidents of human rights violations and address them.
Is the successor body to the UN Commission on Human Rights.
Forty-seven nations sit on the council, elected by regional groups from Africa, Latin America, the West, Eastern Europe and Asia.
Has no power to enforce findings and instead reports to General Assembly.
The US was elected alongside Belgium and Norway to join the Western States bloc of nations sitting on the council.
Bangladesh, Cameroon, Djibouti, Hungary, Jordan, Kyrgyzstan, Mauritius, Mexico, Nigeria, Senegal, and Uruguay will also join the 47-nation council for a three-year period.
The council was set up three years ago to replace the UN Human Rights Commission, which was widely criticised for failing to overcome political alliances and take a strong stand on issues including China's rights record.
But the new council has also been criticised by the US for focusing on Israel and its treatment of the Palestinians and not taking a strong enough stand against violence in Tibet and Darfur.
Human Rights Watch has condemned the trading of votes for seats on the Human Rights Council as unacceptable.