The world number one, whose eight-year reign in the principality ended last year, conceded an early break but eventually proved too much to handle for Gabashvili on centre court.
Nadal, who is on a 29-match winning streak on clay, fell 2-0 down but the Spaniard levelled in the sixth game by breaking to love.
The contest effectively ended there as Gabashvili failed to keep pace with the powerful left-hander.
Eight-times French Open champion Nadal, who has a 49-2 record in Monte Carlo after losing to Serb Novak Djokovic in last year's final, next faces Andreas Seppi of Italy.
Earlier, former world number one Roger Federer barely broke sweat as he breezed into the third round with a 6-1 6-2 thrashing of Czech Radek Stepanek.
The Swiss, who has a record 17 grand slam titles, will face another Czech, Lukas Rosol, after dismissing the experienced Stepanek in less than an hour on the Monte Carlo Country Club's clay.
Fourth-seeded Federer, back in the principality for the first time since 2011, saved two break points and claimed his opponent's serve four times in a quick master class.
"I had a good start to both sets, then I was solid on my own service games. The next thing you know, you're in the lead and you can hit freely," said Federer.
"It was clearly a good match to start my claycourt campaign."
Earlier, eighth seed Milos Raonic of Canada was made to work to overcome South Korea's Yen-hsun Lu 6-7(4) 6-2 6-1.
Swiss third seed and Australian Open champion Stanislas Wawrinka will face big-serving Croatian Marin Cilic.