The National Assembly voted 164 to 20 in favour of Lee, a journalist-turned-politician, as new prime minister, amid a boycott by the conservative opposition Liberty Korea Party (LKP).
All 107 lawmakers of the LKP stayed away as the motion to endorse the prime minister-nominee was put to a vote.
Lee has been dogged by allegations, among other charges, that his wife used a false adress in 1989 to get assigned to a school in Seoul as a teacher.
Under South Korea's strong presidential system, the prime ministerial job is largely symbolic and ceremonial.
Park has been impeached and arrested over a corruption scandal that saw millions of protesters taking to the streets.
Moon has already named ministers for key posts, including the head of the country's spy agency, the foreign minister and economic ministerial posts.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
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