Big crowds, undaunted by the Boston Marathon bombings last week, lined the route to cheer on the runners, many of whom wore black ribbons to honour those killed and wounded in the American race.
Kebede, who was not selected for London 2012, overhauled his Kenyan rival Emmanuel Mutai in the final kilometre to win in two hours six minutes four seconds and must surely have secured a place on the list for August's world championships in Moscow.
Britain's Olympic 5,000 and 10,000 metres champion Mo Farah had dropped out of the race at the halfway stage as planned.
"Many athletes ran 2:04, because of that they selected them (for the London Olympics)," Kebede told reporters. "In October I went away, won (in Chicago), ran a personal
(best) time (2:04:38) and now I win again this competition.
"I'm happy. Maybe I think I'll run in the world championships," the Ethiopian, also champion in 2010, added with a smile.
Jeptoo had, at least, made it to the London Games but was pipped to women's marathon gold by Ethiopia's Tiki Gelena by five seconds.
This time, however, the Kenyan was not prepared to race it out at the end of the 42.195-km slog around London's streets and after pushing the pace at around 30km, she ran solo up the Mall to win in 2:20.15.
The injection of pace proved too much for Jeptoo's only companion, world champion and compatriot Edna Kiplagat, who began to lag and finished more than a minute behind in second.
"Today I'm very happy because I won this year in London," Jeptoo, who has finished in the top three in her eight marathons, told a news conference.
"I knew I was strong because I have done good training so I was having a feeling that I could do it."
Gelena, making her debut in the London Marathon, came a cropper after colliding with a wheelchair racer at a drinks station at 15 km and did not feature among the leaders after halfway, eventually finishing 16th - her shoulders rolling as she laboured to the line.
Men's Olympic champion Stephen Kiprotech of Uganda also had a disappointing debut, finishing sixth after struggling to keep up with the blistering pace set in the first half of the race, which put paid to world-record holder Patrick Makau, who was 11th.
Britain's double Olympic track champion Mo Farah kept up with the leaders for the first half of the race before dropping out as planned soon after the athletes crossed Tower Bridge.
Farah, who will make his marathon debut in next year's race, was greeted with a huge cheer from the crowd as he stepped behind the barriers.
A 30-second silence in tribute to the Boston victims was held before the men's and the mass start. London had deployed extra police in the wake of last Monday's two explosions near the Boston finish line which killed three people and wounded 176.
Some 36,000 fun runners, many of them in fancy dress, began the race in the London sunshine.
The crowds enjoyed a spectacle of speed and endurance as the men's pacemakers set off inside world-record time and the leaders reached the halfway point in 1:01:34.
Stanley Biwott, winner of the 2012 Paris Marathon, was six seconds clear at 35 km but his lead was short-lived and he was caught by Mutai who swept past his Kenyan team mate and kept on going.
It looked a decisive move by Mutai, who set the course record of 2:04:40 when winning in 2011, but Kebede found a second wind and made his way through the field as they drew closer to the line to give the spectators a thrilling finish.
"It was around 40km, when I passed everybody, (that I thought I could win)," said Kebede.
"When I caught Emmanuel, I did not believe it. I was asking how many in front of me and was happy catching them one by one."
Kebede, arms pumping and running with a steady rhythm, passed Mutai in the final kilometre.
"I'm very disappointed. I had some trouble with my hip and thigh," said Mutai.
"I thought I might win today but could not pick up the pace in the late stages."
1. Tsegaye Kebede (Ethiopia) 2:06:04
2. Emmanuel Kipchirchir Mutai (Kenya) 2:06:33
3. Ayele Abshero (Ethiopia) 2:06:57
4. Feyisa Lilesa (Ethiopia) 2:07:46
5. Wilson Kipsang Kiprotich (Kenya) 2:07:47
6. Stephen Kiprotich (Uganda) 2:08:05
7. Yared Asmerom (Eritrea) 2:08:22
8. Stanley Biwott (Kenya) 2:08:39
9. Hafid Chani (Morocco) 2:09:11
10. Ayad Lamdassem (Spain) 2:09:28
1. Priscah Jeptoo (Kenya) 2:20:15
2. Edna Ngeringwony Kiplagat (Kenya) 2:21:32
3. Yukiko Akaba (Japan) 2:24:43
4. Atsede Baysa (Ethiopia) 2:25:14
5. Meselech Melkamu (Ethiopia) 2:25:46
6. Florence Kiplagat (Kenya) 2:27:05
7. Mai Ito (Japan) 2:28:37
8. Alevtina Biktimirova (Russia) 2:30:02
9. Susan Partridge (Britain) 2:30:46
10. Irvette van Zyl (South Africa) 2:31:26
- Sports & Recreation
- Athletics, Track & Field
- Emmanuel Mutai