Premiership leaders Chelsea had to show patience and perseverance to beat a determined Middlesbrough side courtesy of a goal by captain John Terry.
Terry headed in a second-half Damien Duff corner after Fabio Rochemback fumbled an attempted goal-line clearance into his own net.
Rochemback had earlier cleared a similar effort to safety as the visitors frustrated the home side.
Jimmy Floyd Hasselbaink missed Boro's best chance when his shot hit the post.
Chelsea had struggled to break the shackles applied by Boro early on and were fortunate not to be behind when Hasselbaink's chance came after 14 minutes.
Boro striker Yakubu's shot deflected off Terry to ex-Blues striker Hasselbaink and he looked set to score only for his sidefooted effort to come back off the post.
Hasselbaink missed a great chance to put Boro ahead
The scare proved a wake-up call for Chelsea who almost took the lead at the other end when Damien Duff's corner was scrambled away by a desperate Boro defence.
Chelsea appealed for handball against Gareth Southgate but, even though the incident was more ball to hand, it was the first of many escapes for the visitors.
The Boro backline was breached by Frank Lampard and it looked ominous for Steve McClaren's side as the midfielder had a free shot from 18-yards.
But the trademark Lampard long-range strike was straight at keeper Mark Schwarzer, who was quickly in action again when he had to crucially come out and save at the feet of Didier Drogba.
A Terry header from another Blues corner was cleared off the line by Rochemback while Lampard slid in to meet an Arjen Robben cross but saw his shot go wide.
Boro could not be faulted for their work-rate and, after weathering the Chelsea storm, frustrated the champions with their defensive discipline either side of half-time.
But Boro's resistance was eventually broken when Terry, making his 250th club appearance, got his head to another Duff corner and, although Rochemback was again on the line, he only helped the ball into his own net.
Drogba could have extended Chelsea's lead but shot over from just eight yards after some wing wizardry by Duff on the right.
In the end, the miss did not prove costly as they secured their 13th top-flight win of the season.
Chelsea manager Jose Mourinho:
"It was very difficult. They started well and they had a big chance to score before us.
"After that we dominated and had more chances but they were always organised.
"In the second half we scored and had chances through Didier Drogba and Frank Lampard to kill the game but didn't."
Middlesbrough boss Steve McClaren:
"We were disappointed with the result. Sometimes you don't get the result that the performance deserves.
"We showed fantastic attitude and character. We played to win and very nearly did it.
"I think Chelsea will admit it was probably one of their toughest afternoons here for a long time."
Chelsea: Cech, Gallas, Ricardo Carvalho, Terry, Del Horno, Robben (Wright-Phillips 74), Gudjohnsen (Geremi 64), Essien, Lampard, Duff, Drogba (Carlton Cole 78).
Subs Not Used: Paulo Ferreira, Cudicini.
Goals: Terry 62.
Middlesbrough: Schwarzer, Bates, Southgate, Riggott, Pogatetz, Morrison (Queudrue 81), Rochemback, Boateng, Doriva, Yakubu, Hasselbaink (Viduka 72).
Subs Not Used: Ehiogu, Jones, Johnson.
Ref: M Riley (W Yorkshire).