| Date: | 5–11 February |
| Edition: | 3rd |
| Category: | ATP World Tour 250 series |
| Prize Money: | €501,345 |
| Draw: | 28S / 16D |
| Surface: | Hard / indoor |
| Location: | Sofia, Bulgaria |
| Venue: | Arena Armeec |
| Champs: |  Mirza Bašić[1] |
| Champd: | Robin Haase / Matwé Middelkoop[2] |
| Main Name: | ATP Sofia Open Sofia Open |
| Before Name: | Garanti Koza Sofia Open |
| After Name: | Sofia Open |
The 2018 Sofia Open (also known as 2018 DIEMA XTRA Sofia Open for sponsorship reasons)[3] was a men's tennis tournament played on indoor hard courts. It was the third edition of the Sofia Open as part of the ATP World Tour 250 series of the 2018 ATP World Tour. It took place at the Arena Armeec in Sofia, Bulgaria, from 5 February until 11 February 2018. Unseeded Mirza Bašić, who entered the main draw as a qualifier, won the singles title.[4]
See main article: article and 2018 Diema Xtra Sofia Open – Singles.
Mirza Bašić defeated 
Marius Copil, 7–6(8–6), 6–7(4–7), 6–4See main article: article and 2018 Diema Xtra Sofia Open – Doubles.
Alexander Peya, 5–7, 6–4, [10–4]| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q | width=85 | Q2 | width=85 | Q1 |
| Singles | 250 | 150 | 90 | 45 | 20 | 0 | 12 | 6 | 0 | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubles | 0 |
| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q2 | width=85 | Q1 |
| Singles | €85,945 | €45,265 | €24,520 | €13,970 | €8,230 | €4,875 | €2,195 | €1,100 | ||
| Doubles | €26,110 | €13,730 | €7,440 | €4,260 | €2,490 | |||||
| Doubles prize money per team | ||||||||||
| width=70 | Country | width=175 | Player[5] | Rank1 | Seed |
|---|---|---|---|---|---|
| Stan Wawrinka | 15 | 1 | |||
 France | Adrian Mannarino | 25 | 2 | ||
 Luxembourg | Gilles Müller | 28 | 3 | ||
| Philipp Kohlschreiber | 36 | 4 | |||
| Robin Haase | 42 | 5 | |||
 Serbia | Viktor Troicki | 67 | 6 | ||
| João Sousa | 68 | 7 | |||
 Russian Federation | Evgeny Donskoy | 71 | 8 |
The following players received wildcards into the singles main draw:
The following players received entry from the qualifying draw:
The following players received entry as a lucky loser:
Matthew Ebden →replaced by Florian Mayer
Chung Hyeon (blisters) →replaced by Blaž Kavčič Filip Krajinović →replaced by 
Marcos Baghdatis
Mikhail Kukushkin →replaced by 
Salvatore Caruso
Malek Jaziri| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
 Poland | Marcin Matkowski |  Pakistan | Aisam-ul-Haq Qureshi | 67 | 1 | |
| Nikola Mektić | Austria | Alexander Peya | 80 | 2 | ||
| Nicholas Monroe | Australia | John-Patrick Smith | 97 | 3 | ||
| Robin Haase | Matwé Middelkoop | 101 | 4 |
The following pairs received wildcards into the doubles main draw:
The following pair received entry as alternates:
