The pair will join veteran coaches of the UK version of the singing competition, Will.i.am and Sir Tom Jones.
Jennifer, who is also a coach on the American show, is said to be getting a big pay rise for her second series.
"Jennifer was a huge part of the last series," a source said this weekend. “The bosses loved her charisma and the expertise she brought to the table."
The insider told The Sun newspaper: “There was no chance they were going to risk her leaving.”
While Jennifer is back, her fellow newbie Gavin Rossdale will not be.
Olly Murs will replace Gavin on The Voice UK in 2018, it's been claimed.
Gavin confirmed his exit earlier in 2017 after just one series, telling the Metro newspaper: "It’s okay, it’s showbiz. I’m fully grown, I understand how it works."
Gavin added: "It’s such a massive show and it’s great to be part of a juggernaut. I’m going to miss that side of it because that was a real laugh.
"It was a great experience. I had an amazing time on the show I loved it, I love all the people on there. Especially Tom."
The Sun says that none other than former finalist and one-time co-host of X Factor Olly Murs is replacing Gavin.
“It’s a huge coup for The Voice to have Olly on board," an insider told the tabloid today. “He’s got talent show experience, comedic charm and a huge fanbase. His personality will shine through as a coach.
“It won’t be like when he presented X Factor when he had to remain impartial.”
As yet, ITV have officially confirmed no names for The Voice UK next year.
The show will return in January 2018 on ITV for the second of a three-series deal.
As we reported last week, filming of the blind auditions begins later in October.