Aljazeera said on Friday Sir David, who broadcast his final Breakfast with Frost programme for the BBC in May, would be among the "key on-air talent".
Frost was quoted as saying he felt "excitement" about his new role.
"Most of the television I have done over the years has been aimed at British and American audiences," he said.
"This time, while our target is still Britain and America, the excitement is that it is also the six billion other inhabitants of the globe."
Frost's interview shows have attracted world leaders. He notched up 500 editions of Breakfast with Frost before bowing out.
An Aljazeera statement called Frost "the only person to have interviewed the last seven presidents of the United States and the last six prime ministers of the United Kingdom".
It said: "(He) has joined the line-up of key on-air talent at the new 24-hour English language news and current affairs channel."
Frost first came to prominence on television in the early 1960s, when he presented the satirical BBC show That Was the Week that Was.
Aljazeera's English news online
will be distributed in Japan soon
He presented a series of news and current affairs programmes in the UK and America.
Frost's interviews with Richard Nixon after Watergate were revealing, much acclaimed and achieved the largest audience for a news interview in history.
He worked for ITV breakfast station TV-am in the 1980s before rejoining the BBC in 1992.
Earlier this week, flamboyant Japanese internet tycoon turned politician Takafumi Horie said he will take Aljazeera to Japan, hoping to provide a greater variety of views to the public.
The 32-year-old entrepreneur on Monday said his firm, Livedoor, which offers a portal site much like Yahoo! along with other internet services, had signed a deal with Aljazeera to distribute its English news online in Japanese.
Horie unsuccessfully ran for parliament backing the agenda of Prime Minister Junichiro Koizumi, one of US President George Bush's closest allies.
In September Aljazeera launched an Arabic-language children's channel as part of its expansion plans.
JCC, as the channel is called, will produce 40% of its own programmes, a ratio touted as being one of the highest of any children's channel worldwide.
In recent months Aljazeera has
launched three new channels
"Through the concept of 'Edutainment', JCC opens up avenues for Arab children to learn about different environments and cultures," the channel said at its inauguration. "It also helps them develop self-esteem, respect their traditions and values, appreciate people around them and develop a passion for learning."
Based in the Qatari capital Doha with a staff of around 235, JCC will feature a range of programmes for children aged between three and 15.
The channel will air regular debates covering issues facing Arab children as well as productions on health, science and current affairs.
Aljazeera, launched in 1996 in Qatar, also has a sports channel and one dedicated to covering live events without a presenter.