Henin was twice a beaten finalist on the grass at Wimbledon in 2001 and 2006
Justine Henin's first match on grass since 2007 ended with a 6-4 6-2 victory over Angelique Kerber in the Unicef Open at 's-Hertogenbosch in Holland.
The 28-year-old Belgian, who ended a two-year retirement earlier this year, is the top seed for the event and easily defeated the unseeded German.
Another former world number one, Ana Ivanovic, overcame a slow start to oust Sofia Arvidsson of Sweden 4-6 6-0 6-1.
The 22-year-old, unseeded for the tournament, won in one hour 12 minutes.
Henin has enjoyed previous success in this event, winning in 2001 and finishing runner-up two years later.
Her last appearance on grass was in the Wimbledon semi-finals of 2007 when she was beaten in three sets by Marion Bartoli.
Meanwhile in the men's event Igor Sijsling of the Netherlands defeated compatriot and sixth seed Thiemo de Bakker 4-6 6-2 7-6 (7-4) and Belgian Xavier Malisse beat American lucky loser Rajeev Ram 6-3 6-2.