The 24-year-old midfielder joined Mainz as a 13-year-old and progressed through the club's academy before establishing himself in the first team. His journey has included a two-year loan spell at Karlsruher SC, but he has otherwise remained closely connected to the Bundesliga side.
Mainz announced the extension without disclosing its duration. The agreement ensures the club have secured the future of a player who has come through their own development system and become an established member of the senior squad.
Nebel has made 78 Bundesliga appearances for Mainz, scoring 15 goals. He has also featured 10 times in the UEFA Conference League and seven times in the DFB-Pokal, taking his overall record for the club to 15 goals and 18 assists across those competitions.
The midfielder was delighted to continue his association with the club.
"Mainz 05 is my footballing home. I grew up at this club, spent some of the most important years of my development in the academy and worked my way up to becoming a Bundesliga player," he said.
"I'm really happy that I have the trust of the people in charge and that we can continue this journey together. I'm highly motivated to repay that trust with my performances and give everything for the club and our fans."
Nebel's progress has not been entirely straightforward this season. An injury has restricted his involvement since the summer break, limiting him to three Bundesliga appearances at the time of the original report.
Primarily an attacking midfielder, he can also operate out wide, giving Mainz another option across the forward positions. His versatility and familiarity with the club have helped make him an important part of their squad.
He has also been recognised at international level, having previously received a call-up to the senior Germany squad, although he is yet to make his debut.
For Mainz, the extension represents a commitment to a player whose development has been closely tied to the club. For Nebel, it is an opportunity to continue building his career at the place he regards as home.