The Australian sixth seed, who ended an 18-month title drought by winning the Stella Artois tournament last month, was far from his best on court one and very nearly allowed Ferrer to come back from a two-set deficit.
Having been drawn in the opposite half of the draw from his nemesis Roger Federer, however, the 25-year-old Hewitt will fancy his chances of reaching his second Wimbledon final, having won here in 2002.
Next up for Hewitt will be 21-year-old Cypriot Marcos Baghdatis, who outplayed Briton Andy Murray in three sets to reach the last eight.
Hewitt raced into a 5-1 lead, more by virtue of his opponent's mediocrity than his own inspiring tennis, before promptly falling asleep and allowing the 23rd seed to snatch the next three games.
Hewitt started out of his slumber to serve out the opener at the second attempt but the soporific tennis hardly improved in the second set.
Ferrer, one of a record three Spanish players in the last 16, was the more aggressive player with Hewitt, true to form, content to wait for an error from his opponent.
He almost paid for his lethargy at 3-4 when he fell behind 15-40. He saved the first break point with a trademark lob and Ferrer blazed a forehand long on the second.
Ferrer had a third break point in the game but again failed to convert.
In the following game he tamely lost his serve to another Hewitt lob.
It was all getting too much for Ferrer and he was handed a warning for an audible obscenity during the changeover, a consequence of an earlier overrule on a Hewitt first serve that provoked a brief verbal volley between the players.
Having secured a two-set advantage Hewitt dropped serve early in the third and never really recovered. Ferrer sensed his chance to extend the contest.
Hewitt found himself in trouble in the fourth set when Ferrer broke to lead 3-1, the Australian struggling to contain the Spaniard's heavy hitting, particularly a whipcrack of a forehand that pummelled the corners.
Ferrer's big weapon proved his undoing when he netted a routine forehand to gift Hewitt the break back in the next game and from then on Hewitt took charge.
Hewitt let out a bellowing “Come On” when he broke again at 5-5 and he wrapped up the 25th victory of his Wimbledon career when Ferrer dumped a tame volley into the net.
Results:
Men's (fourth round): 1-Roger Federer (Switzerland) beat 13-Tomas Berdych (Czech Republic) 6-3 6-3 6-4; 18-Marcos Baghdatis (Cyprus) beat Andy Murray (Britain) 6-3 6-4 7-6(2); 6-Lleyton Hewitt (Australia) beat 23-David Ferrer (Spain) 6-4 6-4 4-6 7-5; Jonas Bjorkman (Sweden) beat Max Mirnyi (Belarus) 6-3 7-6(6) 4-6 2-6 6-3; 14-Radek Stepanek (Czech Republic) beat 28-Fernando Verdasco (Spain) 6-7(4) 6-3 4-6 6-4 6-2.
Women's: 1-Amelie Mauresmo (France) beat 19-Ana Ivanovic (Serbia and Montenegro) 6-3 6-4; 9-Anastasia Myskina (Russia) beat 26-Jelena Jankovic (Serbia and Montenegro) 6-4 7-6(5); 2-Kim Clijsters (Belgium) beat Agnieszka Radwanska (Poland) 6-2 6-2; 27-Na Li (China) beat 10-Nicole Vaidisova (Czech Republic) 4-6 6-1 6-3; 4-Maria Sharapova (Russia) beat 16-Flavia Pennetta (Italy) 7-6(5) 3-6 6-3; Severine Bremond (France) beat 18-Ai Sugiyama (Japan) 7-6(11) 6-3; 3-Justine Henin-Hardenne (Belgium) beat 15-Daniela Hantuchova (Slovakia) 6-3 6-1; 7-Elena Dementieva (Russia) beat Shenay Perry (U.S.) 6-2 6-0.—Reuters