Her first coach Bart Van Kerckhoven recalled that she was extremely energetic and never wanted to leave the tennis court, adding that, "If the group before her did some sprints to finish off the session, Kim would join in.

At the very end of 1997, she partnered with Zsófia Gubacsi to win her first ITF title in the doubles event at the Grade A Orange Bowl, one of the highest level junior tournaments.

[12] As a fourteen year old, Clijsters could only enter professional tournaments through qualifying since the WTA Tour's policy did not allow players her age to receive main draw wild cards.

In August 1997, Clijsters qualified for her first main draw at her second career tournament on the lower-level ITF Women's Circuit, which was held in the Belgian coastal town of Koksijde.

Both Dominique Van Roost and Sabine Appelmans had been ranked in the top 20 within the previous two years, complementing the rise of Clijsters and Henin on the junior tour.

This success helped lead to the revival of the only WTA tournament in Belgium, which was relaunched as the Flanders Women's Open in Antwerp after not being held in six years.

Clijsters made her WTA debut at the tournament in May, entering the main draw as a lucky loser after losing in the final round of qualifying.

[5][23][24] Clijsters also had a good showing at the US Open, losing to the eventual champion Serena Williams in the third round after squandering a chance to serve for the match.

She won the title with relative ease in just her fourth career WTA event, taking affinity for the friendly atmosphere of the smaller tournament and the faster carpet courts.

[21] Although Clijsters did not reach another Grand Slam quarterfinal the rest of the year, she won three more titles leading up to the year-end WTA Tour Championships in Los Angeles.

Clijsters made it to the final with ease after dropping only six games in the first three rounds, including a victory over Henin in the quarterfinals[40] and a retirement due to injury from Venus Williams in the semifinals.

[52] After losing in the semifinals at Wimbledon to Venus Williams,[53] Clijsters rebounded to win two Tier II titles at the Stanford Classic[54] and the Los Angeles Open.

[21][61] She finished her season by defending her title at the WTA Tour Championships in the first year where the tournament switched to a round robin format in the initial stage.

[74] After Clijsters withdrew from the Indian Wells Open following one match with a torn left wrist tendon, she only played in two more WTA events the remainder of the season.

[21][78] Clijsters was unable to continue her success into the clay or grass court seasons, winning just one title and losing in the fourth round in three sets to Davenport at both the French Open and Wimbledon.

[92] Although she recovered from those issues in time to reach the semifinals at the Australian Open, she needed to retire from that match as well after twisting her ankle while down a break in the third set against Amélie Mauresmo.

[96] While she was healthy enough to play a regular schedule during the clay and grass court seasons, Henin continued her recent dominance of their rivalry over this stretch.

"[111] Nearly two months after her father's death, it was announced that Clijsters would play in an exhibition in May with Tim Henman against Steffi Graf and Andre Agassi to test the new retractable roof on Centre Court at Wimbledon.

[112] In March 2009, Clijsters stated that she was planning to come out of retirement, motivated by returning to the "training schedule from [her] pro days" to prepare for the Wimbledon exhibition.

[157] Her career ended with a second round mixed doubles loss alongside Bob Bryan to the eventual champions Ekaterina Makarova and Bruno Soares, at which point she officially retired.

[159] She played her first tournament of the year at the Chicago Fall Tennis Classic, having accepted a wildcard, but lost in the first round to Hsieh Su-Wei in three sets.

The winners of the round robin groups in April would compete with the defending champion United States team in a knockout format for the title in November.

[165] Although Henin missed the semifinal, Clijsters and Kirsten Flipkens were able to lead Belgium to a victory over the United States, who were also short-handed without Lindsay Davenport or the Williams sisters.

[75] However, she had announced before the year began that she did not intend to compete at the Games because Adidas was the Belgian team's uniform sponsor and her contract with Fila forbade her from wearing clothing from another company.

[152] At the time, she did not have good results at her most recent tournaments, withdrawing from the Rosmalen Grass Court Championships in the semifinals in June due to injury and suffering a lopsided loss in the fourth round at Wimbledon.

A total of 35,681 people attended the match, breaking the world record of 30,472 set in 1973 by the Battle of the Sexes between Billie Jean King and Bobby Riggs.

[207] The three titles she won at the WTA Tour Championships are tied for the fifth-most in history behind only Martina Navratilova, Steffi Graf, Serena Williams, and Chris Evert.

It was reported that De Hous left because he was unhappy with only receiving a $7,500 bonus from her $2.2 million in US Open prize money; however, he denied this was his only financial compensation and attributed his departure to wanting to "take on new challenges" after all of their success in 2005.

They won their opening match against Selima Sfar and Caroline Vis before losing to the second-seeded team of Émilie Loit and Petra Mandula in the next round.

She also occasionally was a commentator at the Grand Slam tournaments, working for the BBC and Fox Sports Australia at Wimbledon and for Channel 7 at the Australian Open.