Clijsters, who missed time while nursing a hip injury, bested Romina Oprandi of Switzerland 6-7 (5-7), 6-2, 6-3 on the grass courts at Autotron Rosmalen in the Netherlands.
Joining her with a Day 1 victory was fourth-seeded Flavia Pennetta of Italy, who rallied for a 2-6, 6-1, 6-1 win over Olga Govortsova of Belarus.
Also notching a victory at the Wimbledon tune-up was Anabel Medina Garrigues of Spain, who dispatched Simona Halep of Romania 7-6 (7-3), 6-2.
Astronomers offer more expansive view of universe
LGBT community has 'bullied the American people': Bachmann