The 2015 Croatia Open Umag (also known as the Konzum Croatia Open Umag for sponsorship reasons) was a men's tennis tournament played on outdoor clay courts. It was the 26th edition of the Croatia Open, and part of the ATP World Tour 250 Series of the 2015 ATP World Tour. It took place at the International Tennis Center in Umag, Croatia, from 20 July through 26 July 2015.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 France | Gaël Monfils | 17 | 1 | |
 Spain | Roberto Bautista Agut | 23 | 2 | |
 Italy | Andreas Seppi | 26 | 3 | |
 Austria | Dominic Thiem | 28 | 4 | |
| Italy | Fabio Fognini | 33 | 5 | |
| Philipp Kohlschreiber | 34 | 6 | ||
| Borna Ćorić | 37 | 7 | ||
 Slovakia | Martin Kližan | 38 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry from the qualifying draw:
Pablo Andújar →replaced by Damir Džumhur| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
| Marin Draganja |  Finland | Henri Kontinen | 60 | 1 | ||
 United Kingdom | Dominic Inglot | Philipp Petzschner | 95 | 2 | ||
| Mariusz Fyrstenberg |  Mexico | Santiago González | 98 | 3 | ||
| Spain | Pablo Carreño Busta | Spain | Marcel Granollers | 104 | 4 |
The following pairs received wildcards into the doubles main draw:
See main article: 2015 Croatia Open Umag – Singles.
Dominic Thiem defeated João Sousa, 6–4, 6–1See main article: 2015 Croatia Open Umag – Doubles.
Máximo González / 
André Sá defeated 
Mariusz Fyrstenberg / Santiago González, 4–6, 6–3, [10–5]
