He then joined his old club Köln again, where he made his Bundesliga debut in 2005 and scored his first goal in his second match, against rivals Bayer Leverkusen.

After his club was relegated to the second division, Helmes became one of the most important players for his side, scoring seven times in his first five games of the season and keeping Köln at the top of the table.

The injury kept him out of the squad for the following four months, during which his team performed extremely poorly and lost all chances to return to the first division.

Even though he confirmed that his departure to Bayer Leverkusen would follow the 2007–08 season, Köln coach Christoph Daum still named him captain of the squad in the summer of 2007.

He was later replaced as captain, but nevertheless had a good second half of the season, for which kicker sportsmagazine named him best striker of Germany's second division, ahead of Oliver Neuville, Chinedu Obasi and Demba Ba.

[2] At Leverkusen, Helmes had a good start in the 2008–09 season, despite his injury in June which caused him being out of action for three weeks.

[3] Forming a duo with Stefan Kießling, he scored six goals in the first five games of the season, among them a hat-trick against Hannover 96.

On 31 January 2011, Helmes moved to fellow Bundesliga side VfL Wolfsburg, the champion of 2008–09 for a reported fee of €8 million.

He made his international debut for Germany in a friendly against Denmark on 28 March 2007, being substituted for Jan Schlaudraff in 80th minute.

He was included in Löw's 26-man provisional Euro 2008 squad but was eventually left out in favour of Oliver Neuville.

[20] He was dismissed in September 2023 after a series of disappointing results left Siegen in the bottom half of the league table, with only four points from seven games.