The crowd went wild - except for Nicki Minaj who looked distinctly unimpressed when the camera panned to her while J.Lo was dancing to Anaconda.
Lopez performed double duty - performing and hosting the ceremony - and managed nice costume changes.
Show-stopper: The singer's opening act was one of the major highlights of the night
Elsewhere, One Direction were the toast of the night.
They had a winning start after they were named favourite pop or rock duo or group.
The British boy band sent the crowd in the Microsoft Theatre in Los Angeles wild when they picked up their award from Minaj at the ceremony.
Addressing the packed theatre, Niall Horan said: 'Wow, to say that we have won this award for three years on the bounce is a pretty incredible thing to say and we wouldn't be able to do it without our fans and all the things they have done for us.'
Harry Styles added: 'To everyone who worked with us and has supported us for the last five years, thank you all, you are brilliant to work with and we love you all. And to the fans, thank you.'
Flaunt it: Jennifer and her dancers wore very tight patterned catsuit
Not a fan? Nicki Minaj appeared distinctly unimpressed when the camera panned to her during J.Lo's performance
The boys later got the crowd on their feet again for their performance of their hit single Perfect.
The Weeknd was the first winner of the night, scoring an AMA for best soul or R&B album Beauty Behind The Madness, and thanked his many collaborators including Kanye West, Lana Del Rey and Ed Sheeran.
He collected his gong from Prince, who sported a third eye on his forehead.
Nicki Minaj accepted the award for favourite rap or hip-hop album for The Pinkprint from reality star Kylie Jenner and model Gigi Hadid, saying: 'This award is about fans voting and I feel like I have the best fans on the planet, I know you're out there on the internet and I love you.
'The Pinkprint was the hardest album I've been a part of, to write and perform every night.'
She added: 'Please find your voice and find your purpose before it's too late.'
On stage: The Booty singer added a furry jacket as she performed a sexy dance routine
Meghan Trainor and Charlie Puth excited the crowd when they shared a passionate kiss at the end of their duet on his hit Marvin Gaye.
Trainor began the performance on her own in a raincoat in front of a raining backdrop for a rendition of her single Like I'm Going To Lose You before a curtain was pulled back to reveal Puth on the piano.
After their performance Puth stood up from the piano for a lengthy kiss with Trainor.
Ariana Grande beat Taylor Swift and Trainor to be named favourite pop/rock female artist. She collected the award from singer Paula Abdul, who won the same award in 1990.
After embracing Trainor, Grande stood at the microphone and said: 'Eeeew, I'm crying, I owe a lot of this to my Nana who voted, she told me: 'Ariana, I went on the computer and voted so I think you will win.'
Go J.Lo: The star had the audience in the palm of her hand
Earlier in the show Grande performed her new single Focus for the first time.
Actor Jared Leto moved the crowd to tears when he paid tribute to the people of Paris and victims of violence around the world.
He recalled an impromptu show his band had performed at the Bataclan in Paris, the scene of one of the terrorist attacks ten days ago.
'Seven months later that same venue was under siege, one of a series of attacks that changed the world forever.'
He added: 'Tonight we honour the victims of the unimaginable violence that took place in Paris and around the world.
Sexy: J. Lo got close with her backup dancers as she kicked off the AMAs
Sizzling: The entertainer gave her all as she launched into her energetic dance routine
'France matters, Syria matters, Russia matters, Mali matters, the Middle East matters, the entire world matters and peace is possible.
Introducing Celine Dion for a performance of Edith Piaf's La Vie En Rose, Leto added: 'Many of us here are the sons and daughters of immigrants and Steve Jobs, the son of a Syrian immigrant, and President Barack Obama. The American Music Awards wanted to show its support for the people of France and the entire world.'
Celebrating the 20th anniversary of the release of her album Jagged Little Pill, Alanis Morissette took to the stage to perform her hit You Oughta Know joined by Demi Lovato.
Booty: The host made sure to put her famous figure on full display
