Mikhail Youzhny was the defending champion but lost in the semifinals to top-seeded Marin Čilić.
Čilić went on to win the title by defeating Jürgen Melzer 6–3, 6–1 in the final.

Seeds

Draw

Finals

Top half

Bottom half

Qualifying

Seeds

Qualifiers

Lucky losers

# Dino Marcan # Matteo Viola

Draw

First qualifier

Second qualifier

Third qualifier

Fourth qualifier

References

Main Draw

Qualifying Draw
{{DEFAULTSORT:2013 PBZ Zagreb Indoors - Singles 2013 ATP World Tour, PBZ Zagreb Indoors - Singles Zagreb Indoors, 2013 Singles 2013 PBZ Zagreb Indoors