Hasina is the first prime minister in Bangladesh's history to be elected to a fourth consecutive, and a fifth overall, five-year term.
Her main political rival, the Bangladesh Nationalist Party (BNP) of former prime minister Khaleda Zia, boycotted the election over fears of vote-rigging.
The BNP has long demanded an election under a non-party caretaker administration but Hasina's ruling party rejected the idea as "unconstitutional".
The 76-year old politician took her oath of office from President Mohammed Shahabuddin at the Bangabhaban palace in Dhaka.
She was joined by her new cabinet of 25 ministers and 11 state ministers.
Senior politicians, foreign diplomats and civil and military officials attended the swearing-in ceremony, which was broadcast live by state-run Bangladesh Television and private broadcasters.
Hasina's ruling party won 222 out of the 298 seats in parliament that were up for election on January 7.
Elections for two other parliamentary constituencies were suspended - one because of poll violence that erupted and the other for the death of an independent candidate of natural causes ahead of the vote.
At least one person was killed in violence on the voting day amid the boycott by the BNP and its conservative allies.
The voter turnout was 41.8 per cent compared to more than 80 per cent in the 2018 elections, according to the country's Election Commission.
The BNP, which had called for a general strike on election day, rejected the election as farce.
The government dismissed the opposition's criticism.
Hasina served previously as prime minister from 1996 to 2001, 2009 to 2014, 2014 to 2018 and 2019 to 2023.
