See main article: 2015 PBZ Zagreb Indoors. Marin Čilić was the two-time defending champion, but withdrew before the tournament started due to an arm injury.
Guillermo García-López won the title, defeating Andreas Seppi in the final, 7–6(7–4), 6–3.
See also: 1. Ivo Karlović (second round)
See also: 2. 
Adrian Mannarino (second round)
See also: 3. 
Guillermo García-López (champion)
See also: 4. 
Gilles Müller (second round)
See also: 5. 
Andreas Seppi (final)
See also: 6. 
Mikhail Youzhny (quarterfinals)
See also: 7. 
Viktor Troicki (quarterfinals)
See also: 8. Marcel Granollers (semifinals)
See also: 1. Aljaž Bedene (second round)
See also: 2. 
Farrukh Dustov (second round)
See also: 3. Michael Berrer (qualified)
See also: 4. 
Norbert Gombos (qualifying competition)
See also: 5. Matthias Bachinger (qualified)
See also: 6. 
Illya Marchenko (qualified)
See also: 7. 
Frank Dancevic (qualified)
See also: 8. 
Kimmer Coppejans (first round)