She captured the women's doubles title at the 1998 Australian Open when she was 15 years old, partnered with Martina Hingis.

4 Monica Seles and eighth seed Nathalie Tauziat, the previous year's finalist, before she lost to Steffi Graf in three sets.

In 1999, Lučić achieved her career-best Grand Slam singles performance when she reached the semifinals at Wimbledon, before losing in three sets to Graf.

After 1999, Lučić suffered a series of personal and financial problems and failed to make any further significant impact on the tour.

[12] As a wildcard in the qualifying draw of the Cellular South Cup in Memphis in February, Lučić won one match (defeating Melanie Oudin) before losing in the second round to Natalie Grandin.

Even though she lost the first round to Knapp in the $100k Rome Challenger, she received a qualifying wildcard for the WTA Tour tournament in May at the same city and beat the 65th-ranked player in the world, Elena Vesnina.

In September 2008, Mirjana started working with her new coach Alberto Gutierrez, planning to play a full schedule the following year.

In her first WTA Tour main-draw match since 2007 Indian Wells, she lost to Anne Keothavong in the first round.

Lučić then continued to toil on the ITF Circuit for several years prior to mounting somewhat of a comeback in the 2010 season.

Shortly after, Lučić qualified for the WTA event in Birmingham, going on to win her first main-draw match since 2007 in Indian Wells, this time over Colombian Mariana Duque.

She continued her good form as she defeated fellow Croatian player Karolina Šprem in the second round.

She then fell to third seed Sara Errani in the second round recovering a 2–4 deficit to force a tie-break before falling 0–6, 6–7.

Seeded fifth in the qualifying draw, Lučić defeated both Heidi El Tabakh and Tamaryn Hendler in straight sets, before repeating her Wimbledon victory over Michaëlla Krajicek with a straight-sets win to qualify for the main draw where she lost to Maria Kirilenko.

In the US Open, after winning three qualifying matches to enter the main draw, she beat Alicia Molik to set up a second round clash with No.

Her fortunes began to change during the clay court season where Lučić reached her first WTA quarterfinal in over ten years at the Strasbourg event, losing to Anabel Medina Garrigues.

[16] She then pulled off a huge upset, stunning second-seed Simona Halep in straight sets to win a spot in the round of 16—the best result of her career at this tournament, and her best showing at a Grand Slam since reaching the semifinals at Wimbledon in 1999.

However, only two weeks later, she entered the Quebec City event and reached the singles final, where she pulled off another major upset by beating Venus Williams on 14 September, setting a record for the longest gap between titles in WTA history, as her previous win happened 16 years and four months earlier at the 1998 Bol Ladies Open.

[18] In addition, paired with Czech player Lucie Hradecká, she won the doubles final of the tournament on the same day.

In the fourth round, she defeated qualifier Jennifer Brady in straight sets to advance to the quarterfinals where she pulled another major upset, beating Karolína Plíšková, a heavy favorite to win the tournament in three tight sets where she made her first Australian Open semifinals and her first semifinal appearance since she did so in the 1999 Wimbledon Championships 18 years ago.

[19] In March 2021, Lučić-Baroni announced her continued plans for a comeback in order to conclude her career on her own terms.