The British No 2, who has received a wild card for the National Championships at Telford next week, lost his way in the second set but recovered his poise for a 6-3, 2-6, 6-4 victory.
Henman, who had beaten Gustafsson last year at Wimbledon and at Doha in January, got off to a flying start with an early break. He held for 5-2, saving a break point with an ace, fired another ace and finally clinched the game when Gustafsson sent a forehand over the baseline.
Henman had three set points in the ninth game, but the 30-year-old Swede saved the first two, as Henman double-faulted on the first and was outmanoeuvred by a lob on the second. But the eighth seed won the set in 27 minutes with an ace.
Gustafsson, cheered on by nearly all the crowd in the half-empty Kungliga Tennishalle, kept his composure as the second set stayed with serve, the Swede winning the third and fifth games on aces.
Henman lost the next game as Gustafsson took a 4-2 lead with a huge overhead smash. He then held for 5-3, then broke once again on a passing shot to square the match at one set each from an hour's play.
Gustafsson dropped serve to start the third set as several line calls went against him. The disruption unsettled the Swede and Henman rolled through the final set and advanced to the quarter-finals as he hit a high volley to an empty corner of the court.
The British No 1, Greg Rusedski, who has been troubled by a virus this week, is scheduled to play Frenchman Lionel Roux in the second round today.
Karol Kucera beat the fifth-seeded Thomas Muster 4-6, 6-3 - a defeat which may have ruined the Austrian's chances of reaching next week's ATP World Championship in Germany.
As well as Henman, seven of Britain's top juniors have been given wild cards for the National Championships. They include 16-year-old Simon Dickson of Cheshire and 15-year-old Hannah Collin of Surrey, who are the current 18 and Under National champions, and David Sherwood, who won the Junior Boys' doubles title (with James Trotman) at the Australian Open last January.
NATIONAL CHAMPIONSHIPS (Telford) Wild cards: Men T Henman (Oxon); M Hilton (Cheshire); S Dickson (Cheshire); D Sherwood (Yorkshire). Women S Lydon (Somerset); L Cartwright (Warks); H Collin (Surrey); H Farr (Surrey).Reuse content