While not addressing the turmoil in Bahrain directly, Legend explained he was at the festival "to celebrate art and its power to bring us together and help us see each other's humanity."
"I feel like it's part of my job to express myself freely and passionately about the issues that I care about," he said, as the crowd cheered in support.
"A just society is not one built on fear or repression or vengeance or exclusion, but one built on love," added Legend, who has spoken out in support of freedom of expression and civil rights issues in the United States.
Bahrain, a close U.S. ally that hosts Navy's 5th fleet, has seen nearly daily protests by members of the Shiite majority demanding a greater say in the Sunni-led monarchy. Several thousand protesters have been jailed and dozens killed in the tiny-island nation over the last four years.
The concert was guarded by anti-riot police vehicles outside the entrance to the historic open-air Arad Fort in Bahrain's capital.
Several Bahraini activists took to Twitter to urge Legend to boycott the 10th annual Spring of Culture festival, organized by the Bahrain Authority for Culture and Antiquities.
In a statement to The Independent newspaper before the concert, Legend addressed calls for him to back out of the Bahrain show and said he has "spent quite a bit of time thinking about human rights, civil rights and other issues of justice." He said that he felt participating in the conversation was the best way to drive progress.
Bahrain's leading human rights activist, Nabeel Rajab, took a softer stance toward Legend's visit than others. He told The Associated Press that he is a fan and welcomes Legend to the country, but would also like to introduce him to relatives of political prisoners.
"I am not against any kind of cultural event and I see that the U.S. civil-rights movement is an inspiration to many Bahraini human rights figures", Rajab said.