Lennart Grill

In January 2019, 1. FC Kaiserslautern manager Sascha Hildmann confirmed that Grill would be the starting goalkeeper for the club over Wolfgang Hesl in the second half of the 2018–19 season. He made his debut for Kaiserslautern in the 3. Liga on 26 January 2019, starting in the home match against Sonnenhof Großaspach, which finished as a 2–0 win.

Bayer Leverkusen

On 8 March 2019, it was announced that Grill would sign for Bayer Leverkusen starting from the 2020–21 Bundesliga season on a four-year deal. Grill made his debut for the team on 28 February 2021, by playing the full 90-minutes in a 1–2 home loss to SC Freiburg, when Lukáš Hrádecký continues to recover from the achilles tendon problems.

Union Berlin

On 16 June 2022, Grill moved to Union Berlin on a loan agreement, with Union reserving an option to buy. On 30 March 2023, the loan agreement was made permanent.

Loan to Osnabrück

On 10 July 2023, Grill joined VfL Osnabrück on loan.

Loan to Eintracht Braunschweig

On 4 July 2024, Grill joined 2. Bundesliga side Eintracht Braunschweig on a season-long loan deal. He started the season as the first goalkeeper, but was sent off in the 9th game of the league season against Hertha BSC, and lost his starter spot to Marko Johansson.

Loan to Greuther Fürth

On 22 January 2025, Grill moved on a new loan to Greuther Fürth, also in 2. Bundesliga.

Dynamo Dresden

On 9 July 2025, Grill signed with Dynamo Dresden in 2.…

Grill was included in Germany's squad for the 2016 UEFA European Under-17 Championship in Azerbaijan. The team managed to reach the semi-finals, before losing 1–2 against Spain. Grill made his only appearance of the tournament in the match against Spain, coming on as a substitute in the 80th minute following a red card for starting goalkeeper Jan-Christoph Bartels.

As of match played 30 November 2025