The Beirut-born Londoner's debut album ''Life in Cartoon Motion'' shot to number one in its first week of release, while his single ''Grace Kelly'' maintained its grip on the top slot for a fourth week.
Mika was named best new talent of the year last month when he topped a BBC poll of music critics and broadcasters.
Joining Mika in the album charts were indie rockers Bloc Party at number two with ''A Weekend in the City''.
Chicago punk-pop act Fall Out Boy were also new at number three with their album ''Infinity on High''.
In the singles charts, indie band the Kaiser Chiefs entered at number two with ''Ruby'', taken from their forthcoming album ''Yours Truly, Angry Mob''.
London rapper Just Jack held steady in third place with ''Starz in their Eyes''.
American rock band Fray rose four places to six with ''How to Save a Life'', while US singer Gwen Stefani jumped from 23 to 10 with ''The Sweet Escape'', featuring hip-hop artist Akon.
REUTERS PDM PM0910