Henman, the world No 18, fell 7-6, 4-6, 6-3 to Sebastien LeBlanc, a wild card entry ranked 885 in the world. The 23-year-old LeBlanc repeatedly attacked the net to surprise Henman, the 10th seed, and record the best win of his career.
"Obviously I'm ranked a lot higher than him, but upsets happen and they'll continue to happen," Henman said. "To play as poorly as I did is very disappointing but it's one of those situations which you have to put behind you and look to next week."
This was Henman's first competitive match since playing in the Davis Cup against Ukraine more than a fortnight ago.
Canadian-born Greg Rusedski, the British No 2 and world No 24, did not enter the tournament. On his last appearance in his native land two years ago he was given a hostile reception from a crowd who were bitter that he had changed his allegiance to Britain. Rusedski pulled out of the Newcastle Challenger last week because of a groin injury, but he and Henman are expected to play in the Cincinnati event next week.Reuse content