Harris, the daughter of an Indian immigrant from Chennai, scripted history by becoming the first-ever woman Vice President of the United States. She is also the first female, first Black and first South Asian American vice president.
Harris, the 49th US Vice President, will serve as the deputy of President Joe Biden, 78, who also took the oath of office, becoming the 46th US President.
“I, Kamala Devi Harris, do solemnly swear that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely; without any mental reservation or purpose of evasion; that I will well and faithfully discharge the duties of the office upon which I am about to enter so help me, God,” she said in her oath.
"Ready to serve," she tweeted from her official Twitter account soon after the inauguration.
"For the people—always," Harris tweeted from her personal account before the inauguration.
"I'm here today because of the women who came before me," she said in another tweet along with a video which featured a number of Black women, including her Tamil mother.
Harris took over the office of the US Vice President from 61-year-old Mike Pence. Biden succeeded Donald Trump, 74.
She wore a purple dress designed by two Black designers for the inauguration.
Harris appeared to be wearing an American flag pin on her left-hand lapel and also sported a Black face mask.
Harris is the daughter of an Indian mother and an African-American father from Jamaica.
She was born in Oakland, California, in 1964, to parents who raised her in a bassinet of civilrights activism.
Her mother, Shyamala Gopalan Harris from Chennai, was a breast cancer researcher who died of cancer in 2009. Harris' father, Donald, is a Jamaican American professor of economics.
The couple divorced in 1972.
Harris grew up in the Bay Area but took frequent trips to India to visit extended family. At 12, she and her sister, Maya, moved with their mother to Montreal, where Gopalan Harris had secured a teaching post at McGill University as well as a research position at the Jewish General Hospital.
After graduating from Howard in 1986 for her undergraduate degree and from the University of California's Hastings College of the Law in 1989, Harris passed the bar the following year and joined the Alameda County prosecutor's office as an assistant district attorney. From there, she began her political ascent.
In 2003, Harris won her first race for San Francisco district attorney, becoming the first Black woman to hold such an office in California. In 2010, she became the first Black woman elected as California attorney general, and in 2016, she became only the second Black woman ever elected as a US senator.
“Today, the daughter of an Indian immigrant, who made dosas on the campaign trail, and spoke to her 'chithis' in her nomination speech, took her oath of office as Vice-President of the United States,” Impact executive director Neil Makhija said.
Impact is the leading Indian-American civic organisation.
"The inauguration of Kamala Devi Harris is not only the culmination of an American dream, but marks the launching of millions of new dreams," he said.