The deal, for which no value was disclosed, is the latest in Thorn's continued expansion of its entertainment empire.
Sparrow was founded as a record label in 1976 by Bill Ray Hearn and has since diversified into music publishing, films and videos and book publishing.
The company's list of artists includes Steven Curtis Chapman, Debby Boone, BeBe and CeCe Winans and Susan Ashton. The portfolio includes 'heavy metal' and 'rap' Christian music as well as the traditional gospel songs.
Bril Flint, a spokesman for EMI Music, said: 'Thorn's strategy is to cover all the different sectors of the music business. Christian music is a growing part of the overall market, particularly in the US, and that is the driving factor.'
He said Sparrow was profitiable and had sales of dollars 30m last year.
According to the Recording Industry Association of America, gospel music accounts for 3.5 per cent of total US music purchases, which are valued at about dollars 7.8bn. Like country and western, religious albums are increasingly finding their way into the mainstream pop charts.
Jimmy Bowen, president of EMI's Liberty country and western label, said: 'We intend to launch a broad-based marketing campaign to expand the presence of Christian recordings in mainstream retail outlets.' Mr Bowen becomes joint chairman of Sparrow with Mr Hearn, who remains chief operating officer.
Jim Fifield, head of Thorn's global music operations, said Sparrow would retain control of its list of artists and would continue to operate its distribution network, which serves bookshops and other outlets worldwide.
EMI Music has annual sales of about pounds 1.4bn compared with total Thorn EMI group turnover of pounds 3.9bn.
The group has been heavily restructuring, pulling out of areas including electrical retailing and software to focus more on music and on rentals.
Thorn caused a storm in August when it bought Richard Branson's Virgin Music, the last big independent recording and music publishing company, for pounds 510m. That deal put Thorn among the top three music businesses worldwide.
The group also recently acquired Medley Records in Denmark and the 50 per cent of Chrysalis and SBK that it did not already own.