Kamworor, 23, recovered from a nasty fall at the start before enduring a heavy downpour towards the end to retain his title in 59 minutes and 10 seconds in Cardiff, Wales.
Kamworor’s time was just a second slower than his Championship Record time he recorded in Copenhagen two years ago.
Jepchirchir, 22, needed the last 50m to claim her first major silverware when she brushed aside compatriot Cynthia Limo in 1:07:31 to triumph.
In a repeat of the 2015 World Cross Country Championships and 2016 National Cross Country Championships, Kamworor condemned compatriot Bedan Karoki, who did most of the pacing, to silver in 59:36.
“I said to myself after the start I was not going to give up,” said Kamworor. Kamworor, who becomes the third man in history to retain the world title after Kenya’s Paul Tergat and Zersenay Tadese from Eritrea, and Karoki finally claimed swift revenge against Britain’s Mo Farah who beat them at the 2015 Worlds. Farah, who took bronze in 59:59, becomes the first Briton to finish on the podium in the history of the race.
Kamworor, who is also the World 10,000m silver medallist, shattered the previous Championships Record time of 59:35 set by Tadese in 2009.
It was the first time the Kenyan men were staging a 1-2 finish since 1997 when Shem Kororia, Moses Tanui and Kenneth Cheruiyot claimed Kenya’s only podium sweep.
Simon Cheprot clocked 1:00:12 for sixth while Edwin Kiptoo 1:00:21 finished ninth as Kenya reclaimed the team title they lost to Eritrea in 2014.
Jepchirchir, who was making her second appearance for Kenya after failing to finish the 2014 Africa Cross in Kampala, orchestrated a 1-2-3 finish for Kenya.
Limo, who was making her maiden appearance for Kenya, settled for silver three seconds off the pace as the 2014 World Half silver medallist Marcy Wacera settled for bronze in 1:07:54.
“It feels great to be world champion. I’m delighted Kenya took the first three places,” said Jepchirchir. “I want to run the 10,000m at Rio Olympics.”
It was sweet revenge for Jepchirchir, who had lost to Limo at the Ras Al Khaimah Half Marathon last month. Limo won with Jepchirchir finishing fourth.
Gladys Chesir and 2012 World Half bronze medallist Pascalia Jepkorir finished sixth and seventh in 1:08:48 and 1:09:44 respectively to ensure Kenya retain the team title.
Jepchirchir now joins the likes of Kenyans Tegla Loroupe, Mary Keitany, Florence Kiplagat and Gladys Cherono, who have won the title. The Kenyan women staged a 1-5 sweep at the 2014 Championships.
Back to the men’s race, Kamworor, who fell down on his both knees, was helped back by an Ethiopian athlete as he ploughed back to join leaders Edwin Kiprop, Karoki and Edwin Kipyego as they passed the 5km mark in 14:10 minutes.