Brazilian driver Razia's win was his first since the 2009 Monza sprint race, and his Arden team's first triumph since the 2010 series opener.
Razia led from the outset after Valsecchi (DAMS) got away slowly from pole and slipped to fourth behind Racing Engineering's Fabio Leimer and Coloni's Stefano Coletti.
It did not take long for Valsecchi to make progress, as he benefited from Coletti running wide on lap five, then put a bold move on Leimer into Turn 1 next time around.
But catching Razia proved harder. Although there was a spell going into the final third of the race when Valsecchi was lapping up to a second faster than his 2011 AirAsia team-mate in the race lead, the gap stabilised at five seconds and ultimately Razia managed to edge away again.
Max Chilton jumped to third in the pitstops and then held off Leimer to give Carlin its maiden GP2 podium.
Close behind, Coletti beat leading rookie Felipe Nasr (DAMS) to sixth, as Lotus' Esteban Gutierrez recovered well from his difficult qualifying day to come through to seventh.
Eighth place and reverse grid pole went to Gutierrez's Lotus team-mate Calado, who won a late battle with slow-starter Giedo van der Garde (Caterham). Fabrizio Crestani completed the top 10 for Lazarus on its GP2 debut, fending off a charging Nathanael Berthon (Racing Engineering).
Top 10 qualifier Jolyon Palmer stalled his iSport car on the grid, as did Rapax's Tom Dillmann, prompted an extra formation lap and leaving Palmer only 17th at the finish.
1. L. Razia (Arden)
2. D. Valecchi (DAMS) +7.817
3. M. Chilton (Carlin) +27.366
4. F. Leimer (Racing Engineering) +28.291
5. S. Coletti (Scuderia) +32.217
6. F. Nasr (DAMS) +33.378
7. E. Gutierrez (Lotus) +33.679
8. J. Calado (Lotus) + 36.449
9. G. Van Der Garde (Caterham) +41.519
10. F. Crestani (Lazarus) +43.240