See main article: article and 2018 Croatia Open Umag.
Guillermo Durán and Andrés Molteni were the defending champions, but Durán chose not to participate and Molteni chose to compete in Båstad instead.
Robin Haase and Matwé Middelkoop won the title, defeating Roman Jebavý and Jiří Veselý in the final, 6–4, 6–4.