In doubles, he won his first Grand Slam title at the 2012 Australian Open, along with Indian partner Leander Paes, defeating the Bryan Brothers in the final.

Paes and Štěpánek also won the men's doubles title at the 2013 US Open, defeating Bruno Soares and Alexander Peya in the final.

[4] Štěpánek grew up admiring Czech tennis player Ivan Lendl, particularly noting "he was the one who brought professionalism to the sport with his conditioning.

2006 was Štěpánek's best year to date; he found himself on the verge of getting into the top ten of ATP rankings, as he defeated José Acasuso in the semi-finals of the Masters Series event in Hamburg.

Earlier in 2006, he won his first ATP singles title, beating Christophe Rochus in Rotterdam, but he had yet to progress beyond the third round of a Grand Slam tournament until he got into the quarter-finals at Wimbledon beating Frank Dancevic, Xavier Malisse, Juan Carlos Ferrero and Fernando Verdasco, before he was eliminated by 34-year-old Jonas Björkman, after holding match point at 7–6 in the fourth-set tie-break.

He also made it to the semifinals in the Rome Masters, losing to Novak Djokovic after he retired due to heat exhaustion.

Since he did not have his own tennis gear which got stuck in customs (they were sent from home), he had to borrow a racquet from Novak Djokovic and socks from Andy Murray.

[7] After Andy Roddick pulled out due to injury before his second match, Štěpánek entered the tournament with two round-robin ties to play against Roger Federer and Gilles Simon.

[9] Štěpánek started his 2009 season at the Brisbane International with a new Bosworth racquet, where he claimed his third ATP title after coming back from a set down to defeat Fernando Verdasco in the final.

At the SAP Open in San Jose, he won his fourth ATP singles title, beating American Mardy Fish in a three-set final.

In the Davis Cup first round tie against France, he lost his opening match to Jo-Wilfried Tsonga in straight sets.

However, he regained his confidence and won the doubles rubber the next day and his second singles match against Gilles Simon in straight sets to give the Czech Republic a berth in the quarterfinals.

In the semifinals, Štěpánek battled Ivo Karlović to victory in a marathon opener in which the 82 games played equalled the highest number in a Davis Cup rubber since the introduction of the tiebreak in 1989.

He also teamed up with Tomáš Berdych to reach the doubles quarterfinals, only to lose to eventual champions Jérémy Chardy and Marc Gicquel.

In April 2012, Serbia's Janko Tipsarević defeated him in five sets to level the Davis Cup quarterfinal at 1–1, after a stormy five-hour match.

After the match, Tipsarević accused Štěpánek of using his middle finger inappropriately during their handshake and calling him a "stinky bastard".

Neither this photo nor footage provided by a Czech TV station conclusively support Tipsarević's version of the events.

[20] Štěpánek underwent neck surgery on 21 January to relieve pressure where a disc was pressing on a nerve rendering his right hand numb and weak.

They defeated the top seeds Mike and Bob Bryan in the semifinals, ending their streak of four major titles.

[22] Štěpánek played on the successful Czech Davis Cup that beat the Netherlands at home in the first round and Japan on the road in the quarterfinals.

Štěpánek then had an impressive run in the AEGON Championships, defeating Mikhail Kukushkin, Bernard Tomic, and then 2013's champion Andy Murray.

[23] On 30 January 2016, Štěpánek and his doubles partner, Daniel Nestor, were defeated by Jamie Murray and Bruno Soares in a three-set match in the 2016 Australian Open final.

At 2016 Summer Olympics in Rio de Janeiro, Štěpánek won bronze medal in mixed doubles with partner Lucie Hradecká.

However, unlike most serve and volley players, Štěpánek usually does not employ a Chip and charge form of play when receiving.

His groundstrokes are not exceptionally powerful, but are consistent and accurate on both wings, allowing him to maintain solid ground at the baseline.

If caught up too long in a baseline rally, however, Štěpánek will often place a deep, accurate groundstroke or a drop-shot and come up to the net to volley, finishing off the point quickly.