[4] By winning the 2017 St. Petersburg Open singles tournament, Džumhur became the first player competing under the Bosnia and Herzegovina flag to claim an ATP World Tour title.

In August 2010, by defeating Victor Baluda, Džumhur won the bronze medal in singles event at the 2010 Summer Youth Olympics in Singapore, where he was also a country representative during the Opening Ceremony as a flag bearer for Bosnia and Herzegovina.

In January 2014, Džumhur became the first male Bosnian representative to play in the main draw of a Grand Slam tournament,[17] having reached the third round of the 2014 Australian Open, where he eventually lost to 7th seed Tomáš Berdych.

On the way to this stage, Džumhur defeated Dustin Brown, Niels Desein, Ruben Bemelmans in qualifying competition, before winning against Jan Hájek, and 32nd seeded Ivan Dodig.

[26] Later in June, Džumhur took part in his only matches of the season played on grass surface, losing both of them in three sets – to Ante Pavić in singles and Gero Kretschmer/Alexander Satschko pair in doubles, during 2014 Wimbledon Championships qualifying events.

[27] During his clay-court comeback, Džumhur won in Italy his third title of the season at 2014 San Benedetto Tennis Cup, by beating Andreas Haider-Maurer in the final in straight sets.

[31] His last Davis Cup appearance of the season has ended in three-set defeat to Ričardas Berankis, which sealed victory for Lithuania and left Bosnia and Herzegovina in Group II of the Europe/Africa Zone.

The beginning of April saw Džumhur win three consecutive ATP World Tour 250 matches against Paul-Henri Mathieu, Marcel Granollers and Andreas Haider-Maurer at 2015 Grand Prix Hassan II in Casablanca, which gave him his first ever semifinal appearance on this level, and his ranking subsequently increased to 85th.

For the first time in his career, Džumhur competed in doubles main draw at Grand Slam event – playing alongside Aljaž Bedene, they were defeated by the Steve Johnson/Sam Querrey team, also in straight sets.

He later went to Morocco to play three clay challengers in Kenitra, Mohammedia and Casablanca, winning the last one (defeated Daniel Muñoz de la Nava in three-set final), which gave him highest ever ranking position of 77.

He later moved to Australia, where was defeated in 2016 Apia International Sydney qualifying by Maximilian Marterer, and then was drawn to face Kyle Edmund in the first round of the Australian Open.

Later he qualified for yet another Masters 1000 event that season, losing in the first round of 2016 Internazionali BNL d'Italia to Jérémy Chardy in three sets, while in the meantime he managed to improve his career-best ranking to 71.

On 9 June Džumhur received a Tripartite Commission Invitation, which gave him the right to represent Bosnia and Herzegovina at the 2016 Summer Olympics, as the first male tennis player in country's history.

For the second year running Džumhur took part in the exhibition grass tournament played in June in Liverpool, and after winning both of his singles matches, including Sunday final against Paolo Lorenzi, he was crowned champion.

Then he played in Umag his last clay court ATP World Tour event of the season, defeating Nicolás Almagro and Thomas Fabbiano before losing a three-set quarterfinal battle with Fabio Fognini.

After four consecutive losses Džumhur upset a 17th seed Bernard Tomic in the first round of the ultimate Grand Slam tournament of the season, which was a repeat of the match they played in the previous US Open.

After reaching a semifinal in Alphen aan den Rijn, where Džumhur was forced to retire in the third set due to right shoulder injury, he helped his national team winning 5–0 in Vilnius a Davis Cup tie against Lithuania, notching a straight-set victory over Laurynas Grigelis, which gave Bosnia and Herzegovina a progress to the Europe/Africa Zone Group I for the very first time.

Firstly, at the 2016 Kremlin Cup he came back from 1–4 deficit in the third set versus Karen Khachanov to win 6–4 (despite the Russian was twice serving for the match) and progress to the second round where he was forced to retire against Pablo Carreño Busta due to food poisoning.

On 15 December Džumhur was named by Nezavisne novine readers as Bosnian Athlete of the Year and was presented with the award at the ceremony in Sarajevo organized by the newspaper itself and Radio and Television of Bosnia and Herzegovina.

His poor start to the season continued in Melbourne, where he lost in the first round of the Australian Open to Viktor Troicki, coming back from two sets down before eventually losing in five.

Later he took part in the first ever Europe/Africa Zone Group I Davis Cup tie for Bosnia and Herzegovina, after the promotion sealed in Vilnius in the previous season, facing Poland in Zenica.

Despite fitness problems, Džumhur managed to play and defeat in straight sets Hubert Hurkacz, contributing to a 5:0 win and progress to the second round to face Netherlands at home.

Soon after he went on to play Sofia Open, where he was beaten in his first match by Andreas Seppi, even though the Italian was involved in clay-court Davis Cup tie in Buenos Aires only two days earlier.

Damir's rise of form continued in Delray Beach as he defeated Konstantin Kravchuk and barely lost to Juan Martín del Potro, receiving appraisal for his display from the Argentinian.

After overcoming Thiemo de Bakker in straight sets, in what was called by himself as the best match for Bosnia and Herzegovina he ever played, he has faced Robin Haase in 4th rubber, with Netherlands leading the tie by 2:1.

Damir's attitude was broadly commented as he was involved in multiple arguments throughout the match with chair umpire, ITF supervisor, Haase and other members of Dutch team.

That time he managed to win all five matches and by defeating Calvin Hemery 6–1, 6–3 in the final he claimed his seventh ATP Challenger Tour singles title, moving up to 83rd place.

It was followed by the only grass appearance of the season, at 2017 Wimbledon Championships, where Džumhur firstly notched his most convincing Grand Slam match triumph defeating Renzo Olivo 6–2, 6–0, 6–1, before falling to Aljaž Bedene in four-set second round battle.

Then he was a runner-up in Santo Domingo challenger (lost to Víctor Estrella Burgos) before achieving his career-best result in Winston-Salem, North Carolina, where he defeated Denis Istomin, Gilles Simon, Horacio Zeballos, Hyeon Chung and Kyle Edmund en route to his first ATP Tour final, also becoming Bosnia's first player to reach an ATP World Tour final, where he lost eventually to Roberto Bautista Agut.

After the Australian tour, he reached the quarterfinals of Montpellier as a qualifier, where he lost in straight sets to Filip Krajinović, after beating fourth seed Nikoloz Basilashvili in the round of 16.