Nadal hadn’t played a tennis match since Indian Wells last month when he was forced to withdraw at the semi-final stage with an injury.
But he showed no ill-effects of those knee problems as he outclassed Bautista Agut from the outset.
The 11-time Monte Carlo champion raced away with the first set 6-1 and although Bautista Agut improved in the second set it wasn’t enough to stop Nadal winning 6-1 6-1.
It was Nadal’s 16th straight win at Monte Carlo and he improves to a career 69-4 win-loss record.
And speaking after the match, Nadal was pleased with how he performed.
Nadal told Amazon Prime: "I had great feelings. Always this court is so so special for me.
"I’m enjoying the fact that I have one more time the chance to be playing here in this amazing club.
"I’m just happy for this good beginning [to the tournament]."
When asked if he ever feels like he could have done better despite an exceptional display, he said: “Always yes.
“Especially at the beginning of the clay court season. You are always looking to what you can add.
"I think I did what I had to do today. It was the first match on clay in almost a year so I just tried to play solid and dominant with my forehand when I had the chance.
"Then a couple of times [I had] volleys [at the net] because I was in control of the point.
"So that is good news."
Grigor Dimitrov beat Jan-Lennard Struff 7-6 6-4 and will face Nadal next.