Career
Early career
Sebastian Mielitz began his football career at Eintracht Oranienburg, moving later to MSV Neuruppin and Energie Cottbus. In 2005, he joined the youth team of SV Werder Bremen. On 10 November 2007, he debuted for the second team of Werder Bremen in the second half of a match, replacing the injured first-choice goalkeeper Nico Pellatz.
In August 2008, Mielitz extended his contract until 2010.
His professional debut in the 3. Liga was on 16 August 2008 against SSV Jahn Regensburg.
Werder Bremen
On 3 December 2009, Mielitz made his first appearance with Werder"s first team in a Europe League home match against Nacional, filling in for the injured Tim Wiese. Three days later, on 6 December 2009, he debuted in the Bundesliga in an away match against 1.
Football Club Köln which the match was 0–0 and Mielitz made a good performance and managed to get his first clean sheet.
He also played 90 minutes. Despite this, Mielitz remained a third choice goalkeeper behind Wiese and Christian Vander ahead of the new season and continued so the new season as well. In March 2010, Mielitz signed a contract extension, keeping him until 2012.
On 20 October 2010, Mielitz made his first appearance in the Union of European Football Associations Champions League group stage against Twente, coming on for the injured Wiese and played against them as well in a 2–0 loss on 2 November 2010.
At the end of the season on 27 May 2011, Mietlitz signed another contract extension, keeping him until 2013. Rumors began to leak that Wiese was on the verge of leaving the club with Mielitz as Wiese"s successor.
Ahead of the new season, Mielitz was placed as second choice goalkeeper, taking Vander place and demoting him as a third choice. Mielitz played his first match of the season after Wiese was sent off in the early minutes of a 1–1 draw against 1.
Football Club Nuremberg on 17 September 2011.
With Wiese receiving a three match ban, Mielitz played three games where he showed very good performance until Wiese returned from suspension. Throughout the season, Wiese managed to beat off Mielitz becoming first choice, leaving Mielitz on the substitute bench, but he occasionally got playing time. The following season, Wiese left Werder Bremen to join Hoffenheim and Mielitz took over the number 1 shirt.
Mielitz signed another contract extension, keeping him until 2014.
In the LIGA total! After the match against Bayern Munich, Mielitz said YouTube helped him save a penalty from Schweinsteiger. He was part of the team that participated at the 2009 Fédération internationale de football association U-20 World Cup.