Federer, who won the adidas International and the Tennis Masters Series event in Hamburg, recorded a 6-2, 7-5 win over Krajicek. Last week, Federer reached the semifinals of the Gerry Weber Open before losing to German Nicolas Kiefer in three sets.
Krajicek was playing for the first time since the Tennis Masters Series event in Stuttgart in 2000. Shortly after that tournament, he underwent right elbow surgery and missed all of the 2001 season.
Seventh-seeded Arnaud Clement of France routed Oliver Gross of Germany, 6-0, 6-2 and France's Anthony Dupuis upset eighth-seeded countryman Julien Boutter 6-4, 6-4.
In other men's matches, American Michael Russell beat Raemon Sluiter of the Netherlands, 7-6 (7-4), 6-2; Russia's Mikhail Youzhny breezed past Argentina's Agustin Calleri, 6-3, 6-0; Swiss qualifier Yves Allegro defeated Alex Calatrava of Spain, 6-4, 6-2; and Belgian Christophe Rochus rallied for a 1-6, 6-2, 6-4 win over French qualifier Rodolphe Cadart.
In women's action, fourth seed Elena Dementieva of Russia and No. 8 Martina Sucha of Slovakia each recorded straight-sets wins. Dementieva ousted Spain's Marta Marrero, 7-6 (7-4), 6-3 and Sucha dispatched Barbara Rittner of Germany, 7-6 (7-3), 7-5.
Also, Miriam Oremans of the Netherland beat Eva Dyrberg of Denmark, 6-1, 6-3; Germany's Bianka Lamade cruised past Silvana Bauer of the Netherlands, 6-2, 6-2; Andrea Glass of Germany overcame Rossana Neffa-De Los Rios of Paraguay, 6-7 (4-7), 7-5, 6-4; Russian Elena Bovina beat Germany's Marlene Weingartner, 6-4, 7-5; and Slovakia's Katarina Srebotnik defeated Anca Barna of Germany, 6-3, 6-4.
Defending champion Lleyton Hewitt of Australia and his girlfriend, Kim Clijsters of Belgium, are the top seeds. Hewitt won his third straight Stella Artois Championships on Sunday.
Clijsters lost last year's final here to countrywoman Justine Henin, who is seeded second this week.