It is also Nadal's 11th Monte Carlo Masters title in 14 years.
This is a significant win for the Spaniard as it will help him in retaining his world number one spot.
World No. 36 Nishikori was chasing his first ever Masters title.
The top-seeded Spaniard is now eyeing for his 11th title in the upcoming Barcelona open and then would focus his sights to win the 11th French Open title at Roland Garros. (ANI)