Switzerland's Stan Wawrinka was seeded first, besting seven other competitors, in the 2018 Diema Xtra Sofia Open.
SUI 1 Adrian Mannarino 2 Gilles Muller 3 Philipp Kohlschreiber 4 Robin Haase 5 Viktor Troicki 6 Joao Sousa 7 Evgeny Donskoy 8 Stan Wawrinka 
