The coalition suffered unprecedented losses in the March 8 elections after the opposition wrested control of five states and denied the government its long-held two-thirds parliamentary majority.
For the first time in Malaysia's history, a woman, Wan Azizah Wan Ismail, president of the Keadilan party, will sit as the lead of the opposition in parliament.
She is the wife of Anwar Ibrahim, the former deputy prime minister and de facto leader of Malaysia's loose opposition coalition, Pakatan Rakyat.
Anwar, who was barred from running for office until a legal ban expired on April 14, has claimed he has the support of 30 BN MPs - enough to bring down the government.
Abdullah is resisting pressure to quit over
the election results [Reuters]
The new parliament also includes a record 24 women MPs, including 10 opposition representatives.
Among those sworn in on Monday was Abdullah Ahmad Badawi, the prime minister, along with members of his cabinet.
Abdullah has come under pressure to resign from his post following the coalition's dismal election performance.
Several key leaders in the United National Malays Organisation, the main partner in the ruling coalition, have warned Abdullah that he would lose if he stood for re-election as the party's president later this year.
Nearly two months after the general elections, there have also been signs of possible strains between the BN-run federal government and the newly opposition-controlled states, including the reported shelving of major projects infrastructure projects in Penang and Selangor, the two most developed states now under opposition control.
The federal government has denied claims that it is punishing voters for supporting the opposition and sabotaging development efforts by the new governments.