The 2015 Tilia Slovenia Open was a professional tennis tournament played on hard courts. It was the third edition of the tournament which was part of the 2015 ATP Challenger Tour. It took place in Portorož, Slovenia between 10 – 15 August 2015.
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
 Spain | Marcel Granollers | 74 | 1 | |
 Italy | Paolo Lorenzi | 87 | 2 | |
 Belgium | Kimmer Coppejans | 103 | 3 | |
 Slovakia | Lukáš Lacko | 117 | 4 | |
| Slovakia | Norbert Gombos | 126 | 5 | |
| Italy | Luca Vanni | 140 | 6 | |
| Thiemo de Bakker | 141 | 7 | ||
 Bosnia and Herzegovina | Mirza Bašić | 152 | 8 |
The following players received wildcards into the singles main draw:
Cem İlkelThe following player entered the singles main draw as an alternate:
The following players received entry from the qualifying draw:
Riccardo Ghedin
Joshua Milton Edoardo EreminThe following player entered the singles main draw as a lucky looser:
See main article: 2015 Tilia Slovenia Open – Singles.
Luca Vanni d. Grega Žemlja 6–3, 7–6(8–6)See main article: 2015 Tilia Slovenia Open – Doubles.
Fabrice Martin / 
Purav Raja d. 
Aliaksandr Bury / 
Andreas Siljeström 7–6(7–5), 4–6, [18–16]