The team of Junelle Bromfield, Janieve Russell, Roneisha McGregor and Stephenie-Ann McPherson ran a brilliant race to clock a season-best 3:28.40 pulling away from the Netherlands, who were second in 3:28.57. Poland was a close third, finishing in 3:28.59 in the exciting final track event of the championships.
The win means McPherson finished the championships with two of Jamaica's three medals, 4x400m gold and the bronze medal she won in the 400m on Saturday.
Kimberly Williams won the other medal, a bronze in the Women's Triple Jump on Sunday morning.
Belgium won the men's event in 3:06.52 over Spain (3:06.82) and The Netherlands (3:06.90).
It was a bittersweet day for Jamaica as Natoya Goule, the second-fastest woman in the world over 800m this year, disappointed in the 800m final where she finished fourth.
The race was won by Ajee Wilson in 1:59.09. The silver medal went to Ethiopia's Freweyni Hailu (2:00.54) and Uganda's Halymah Nakaayi (2:00.66).
Grant Holloway found redemption for last year's Olympic disappointment when he crowned himself world champion in the 60m hurdles, clocking 7.39. Frenchman Pascal Martinot-Lagarde took the silver medal in 7.50 while the USA's Jarret Eaton took the bronze in 7.53.
The championships ended with a world record in the men's pole vault as Mondo Duplantis cleared 6.20m to break his own record set two weeks ago.