Rex Features
The girl group, who formed on Popstars: The Rivals, beat competition from fellow musicians Will Young and Leona Lewis to head up the list.
Big Brother contestants Craig Phillips, the late Jade Goody and Chantelle Houghton also made the top 20, while opera singer Paul Potts is the highest-earning Britain's Got Talent star.
Myleene Klass beat former Hear'Say bandmates Kym Marsh and Suzanne Shaw, finishing fifth with a reported £7.5 million fortune.
The list was compiled by Current TV as part of its Desperately Seeking Fame season, which starts tonight at 10pm.
The full reality TV rich list top 20:
1. Girls Aloud - £25million
2. Will Young - £12.5 million
3. Leona Lewis - £10 million
4. Jade Goody - £8 million
5. Myleene Klass - £7.5 million
6. Gareth Gates - £6.5 million
7. Paul Potts - £5 million
8. Craig Phillips - £5 milion
9. Lemar - £4 million
10. Jane McDonald - £3.5 million
11. Liberty X - £3 million
12. Brian Dowling - £2.5 million
13. Ben Fogle - £2 million
14. Kym Marsh - £1.8 million
15. Suzanne Shaw - £1.4 million
16. Abigail Clancy - £1.25 million
17. Charlotte Hobrough - £1.2 million
18. Chantelle Houghton - £1 million
19. Jonny Gibb - £1 million
20. Darius Danesh - £900K
