With hardly a breath of wind on a glorious morning of unbroken sunshine at Riviera Country Club, the 34-year-old American fired a flawless seven-under-par 64 to take control of the US Tour event.
Kuchar made a sizzling start with birdies on his first three holes and picked up four more to finish one ahead of Spaniard Sergio Garcia, who carded a 65 late in the day as fog began to roll across the course.
Play was eventually suspended in fading light with 18 players yet to complete the opening round.
"It was a great day," said four-times US Tour winner Kuchar, who has spent the last three weeks in Palm Springs and Hawaii on a family holiday.
"It's always fun to have bogey-free days, especially around this golf course. I got off to a great start, birdied my first three and all three were kick-in birdies.
"Just drove it well today which is a big key around here. The greens are pretty tricky and pretty firm this year so coming out of the rough, it's difficult to get a ball to stop close to the hole."
Garcia, making his first appearance of the year on the US Tour, was delighted with his round which, like Kuchar's, featured birdies on his first three holes.
"It was nice to start like that," said Garcia who teed off at the par-four 10th. "I hit my drivers pretty good.
"Overall I managed to hit some nice chips and hit some nice putts here and there, so I'm very pleased with the round."
American Brandt Jobe, who is playing the US Tour on a major medical exemption this year because of a lingering neck injury, carded a 66 in only his second tournament since the AT&T National last July.
Briton David Lynn and Americans James Hahn and Charlie Beljan opened with 67s while Riviera fan favorite Fred Couples, a twice champion who is competing in the event for a record 31st time, was among a group of 11 players knotted on 68.
"I actually played very, very well," said the 53-year-old Couples, champion here in 1990 and 1992. "It's always fun playing here.
"Last year I opened up with a 69 and this year with a 68, so I hope to come out and play well tomorrow, hit the ball solid and have another good round."
Twice champion Phil Mickelson, who clinched his 41st US Tour title at the Phoenix Open two weeks ago, offset four birdies with four bogeys to start out with a level-par 71.
"It could have been better but it could have been a lot worse, and I'll certainly take it," the American left-hander said after bogeying his penultimate hole, the par-four eighth.
"I hit the ball pretty solid (in practice) yesterday. I felt like I was on the right track, and when I came out this morning, it was a little bit off.
"I was hitting some pull-hooks, I was hitting some block cuts and so I put myself in some not great spots off the tee. Had to fight to make pars and I'm pretty fortunate, I think, to shoot even par."
Fellow American Bill Haas, who played in the same group with Mickelson, launched his title defense with a 70 while Masters champion Bubba Watson surprisingly struggled to a six-bogey 77.
British world number eight Lee Westwood and American veteran Jim Furyk returned matching 68s while third-ranked Englishman Luke Donald carded a 69.
Donald heads a strong field at Riviera this week which includes 12 of the world's top 20 players, and 25 of the top 50.
- Sports & Recreation
- Sergio Garcia
- Riviera Country Club