Sijsling's first success on the ATP tour came in 2011, when he reached the quarterfinals in Metz, losing to Ivan Ljubičić.

In 2012, he again reached the quarterfinals in s-Hertogenbosch, after beating Jarkko Nieminen and Olivier Rochus in the first two rounds.
He was beaten by David Ferrer.
He qualified for the US Open that year and reached the second round of the main draw, where he again lost to Ferrer.
In Kuala Lumpur, he again reached the quarterfinals, falling yet again to Ferrer.
He reached the second round in Moscow and Paris-Bercy, falling to Andreas Seppi and Janko Tipsarević, respectively.
In doubles, he reached the quarterfinals in Rotterdam, partnering Thomas Schoorel.
He also reached the quarterfinals in Moscow, partnered with Roberto Bautista Agut.
Sijsling's first success on the ATP tour came in 2011, when he reached the quarterfinals in Metz, losing to Ivan Ljubičić.
In 2012, he again reached the quarterfinals in s-Hertogenbosch, after beating Jarkko Nieminen and Olivier Rochus in the first two rounds. He was beaten by David Ferrer. He qualified for the US Open that year and reached the second round of the main draw, where he again lost to Ferrer. In Kuala Lumpur, he again reached the quarterfinals, falling yet again to Ferrer. He reached the second round in Moscow and Paris-Bercy, falling to Andreas Seppi and Janko Tipsarević, respectively. In doubles, he reached the quarterfinals in Rotterdam, partnering Thomas Schoorel. He also reached the quarterfinals in Moscow, partnered with Roberto Bautista Agut.
Igor Sijsling