At the 2019 Australian Open Schwartzman defeated Rudolf Molleker in four sets and American Denis Kudla in a five-set thriller.
He was knocked out in the third round by former Wimbledon finalist, Tomáš Berdych.

Schwartzman then competed in the 2019 Cordoba Open, making the quarterfinals.
Schwartzman went on to make the finals at the 2019 Argentina Open, a clay ATP 250 level tournament.
 Along his way to the finals Schwartzman defeated world #8 Dominic Thiem, 2-6, 6-4, 7-6.
 Schwartzman lost in straight sets to Italian Marco Cecchinato in the finals.

Schwartzman was unable to defend his title at the 2019 Rio Open, retiring in the second set with a right leg injury in the first round.

Schwartzman defeated world #6 Kei Nishikori 6–4, 6–2 in the quarterfinals of the 2019 Italian Open, before being defeated by Djokovic in three sets.

Schwartzman then captured the title at the 2019 Los Cabos Open, defeating Taylor Fritz in the final, 7–6, 6–3.
It marked his first-ever title at a hard court tournament, and third ATP title.

At the 2019 US Open, in the fourth round he upset world #6 Alexander Zverev in four sets, for his sixth career victory against a top-10 opponent.

In 2019, as he had done in 2017, he led all ATP players in percentage of second serve return points won (56.05%).
Career-wise, he was fourth among active players in return games won (31.1%), behind only Nadal (33.5%), Djokovic (32%), and Andy Murray (31.7%).
At the 2019 Australian Open Schwartzman defeated Rudolf Molleker in four sets and American Denis Kudla in a five-set thriller. He was knocked out in the third round by former Wimbledon finalist, Tomáš Berdych.
Schwartzman then competed in the 2019 Cordoba Open, making the quarterfinals. Schwartzman went on to make the finals at the 2019 Argentina Open, a clay ATP 250 level tournament.  Along his way to the finals Schwartzman defeated world #8 Dominic Thiem, 2-6, 6-4, 7-6.  Schwartzman lost in straight sets to Italian Marco Cecchinato in the finals.
Schwartzman was unable to defend his title at the 2019 Rio Open, retiring in the second set with a right leg injury in the first round.
Schwartzman defeated world #6 Kei Nishikori 6–4, 6–2 in the quarterfinals of the 2019 Italian Open, before being defeated by Djokovic in three sets.
Schwartzman then captured the title at the 2019 Los Cabos Open, defeating Taylor Fritz in the final, 7–6, 6–3. It marked his first-ever title at a hard court tournament, and third ATP title.
At the 2019 US Open, in the fourth round he upset world #6 Alexander Zverev in four sets, for his sixth career victory against a top-10 opponent.
In 2019, as he had done in 2017, he led all ATP players in percentage of second serve return points won (56.05%). Career-wise, he was fourth among active players in return games won (31.1%), behind only Nadal (33.5%), Djokovic (32%), and Andy Murray (31.7%).
Diego Schwartzman