2015 Western & Southern Open – Men's singles

Defending champion Roger Federer defeated Novak Djokovic in the final, 7–6(7–1), 6–3 to win the men's singles tennis title at the 2015 Cincinnati Masters. He won the title without losing a set or having his serve broken for the second time, after 2012. It marked the first time Federer defeated the world No. 1 and No. 2 players in consecutive matches en route to a title. It was Djokovic's fifth runner-up finish without winning the title; he would eventually do so in 2018.

Seeds
The top eight seeds receive a bye into the second round.

🇷🇸 Novak Djokovic (final) Roger Federer (champion) 🇬🇧 Andy Murray (semifinals) 🇯🇵 Kei Nishikori (withdrew because of fatigue) Stan Wawrinka (quarterfinals) 🇨🇿 Tomáš Berdych (quarterfinals) Marin Čilić (third round) 🇪🇸 Rafael Nadal (third round) 🇨🇦 Milos Raonic (first round) 🇫🇷 Gilles Simon (first round) 🇺🇸 John Isner (first round) 🇫🇷 Richard Gasquet (quarterfinals) 🇧🇪 David Goffin (third round) 🇫🇷 Gaël Monfils (first round) Kevin Anderson (third round) 🇧🇬 Grigor Dimitrov (third round)

Seeds
• # 🇫🇷 Benoît Paire (qualifying competition, lucky loser)

• # 🇺🇸 Steve Johnson (qualifying competition)

• # 🇨🇦 Vasek Pospisil (qualified)

• # 🇰🇿 Mikhail Kukushkin (first round)

• # 🇺🇦 Sergiy Stakhovsky (moved to main draw)

• # 🇨🇴 Santiago Giraldo (qualifying competition)

• # 🇩🇪 Benjamin Becker (first round)

• # 🇫🇷 Nicolas Mahut (qualified)

• # 🇺🇦 Alexandr Dolgopolov (qualified)

• # 🇺🇿 Denis Istomin (qualifying competition)

• # 🇰🇷 Chung Hyeon (qualifying competition)

• # 🇦🇺 Thanasi Kokkinakis (qualified)

• # 🇺🇸 Denis Kudla (qualified)

• # Lu Yen-hsun (qualified)

• # 🇹🇷 Marsel İlhan (qualifying competition)

Qualifiers
• # 🇺🇸 Denis Kudla

• # 🇫🇷 Nicolas Mahut

• # 🇨🇦 Vasek Pospisil

• # Lu Yen-hsun

• # 🇦🇺 Thanasi Kokkinakis

• # 🇺🇦 Alexandr Dolgopolov

• # 🇩🇪 Alexander Zverev

Lucky loser

 * 1) 🇫🇷 Benoît Paire