Gross has completed his return to the club from German giants Dortmund on a contract until the end of next season.
Brighton boss Fabian Hurzeler welcomed the much loved 34-year-old back to the side as the shock deal was revealed on Friday afternoon.
“We are really pleased to have Pascal back with us.
“He’s a fantastic player and someone I know well and was looking forward to working with when I first came to the club.
“Brighton fans know his attributes, but he brings great leadership qualities to the group. Those qualities, along with his experience and ability, will be a huge asset in the second half of the season.”
Gross, 34, was Brighton's first-ever Premier League signing in May 2017 when he joined the club from FC Ingolstadt for just £3M.
The veteran was Brighton's record Premier League goalscorer with 30 until Danny Welbeck went past him last April will be a welcome return for fans who adore the German star.
The midfielder has made 228 Premier League appearances for Albion, scoring 30 goals and providing 45 assists.