Van der Garde (Caterham) was one of many drivers to run wide on the exit of the final corner and along with Coloni's Stefano Colleti (who set the 12th best time), will have to wait and see if the stewards deem he gained an advantage in doing so on his way to setting his pole lap of 1m42.451s.
Behind him, last week's double winner Davide Valsecchi (DAMS) just pipped Racing Engineering's Fabio Leimer for second.
Max Chilton, quickest in this morning's practice session, was fourth quickest, just ahead of Carlin team-mate Rio Haryanto.
Lotus drivers Esteban Gutierrez and James Calado also lost out as their decision to save a set of tyres by not posting a time in practice failed to pay off. The Mexican was 13th, the Brit down in 22nd.
Luiz Razia (Arden), who is second in the championship standings, was sixth fastest.
1. Giedo van der Garde (Caterham) 1m42.451s
2. Davide Valsecchi (DAMS) + 0.145s
3. Fabio Leimer (Racing Engineering) + 0.168s
4. Max Chilton (Carlin) + 0.177s
5. Rio Haryanto (Carlin) + 0.240s
6. Luiz Razia (Arden) + 0.388s
7. Rodolfo Gonzalez (Caterham) + 0.500s
8. Dani Clos (Addax) + 0.629s
9. Marcus Ericsson (iSport) + 0.673s
10. Tom Dillmann (Rapax) + 0.712s
11. Felipe Nasr (DAMS) + 0.721s
12. Stefano Coletti (Coloni) + 0.755s
13. Esteban Gutierrez (Lotus) + 0.762s
14. Brendon Hartley (Ocean) + 0.768s
15. Fabrizio Crestani (Lazarus) + 0.860s
16. Nathanael Berthon (Racing Engineering) + 0.877s
17. Jolyon Palmer (iSport) + 0.940s
18. Fabio Onidi (Coloni) + 0.996s
19. Nigel Melker (Ocean) + 1.002s
20. Johnny Cecotto (Addax) + 1.148s
21. Julian Leal (Trident) + 1.208s
22. James Calado (Lotus) + 1.306s
23. Simon Trummer (Arden) + 1.478s
24. Stephane Richelmi (Trident) + 1.649s
25. Ricardo Teixeira (Rapax) + 2.399s
26. Giancarlo Serenelli (Lazarus) + 2.585s