Nadal, the 2008 singles gold medallist, will pair up with Alcaraz in a tennis dream team at Roland Garros, looking to also add to the doubles title he won with close friend Marc Lopez at Rio in 2016.
The 22-time Grand Slam champion was keen to play down expectations though ahead of his final Olympics, with Nadal and Alcaraz teaming up for the first time.
"I understand the fascination, the hope of seeing us play together, (but) let's not think that this translates into success, I think that's a mistake," said Nadal.
"At the end of the day Carlos hasn't played much doubles and I haven't played much in either doubles or singles," he said at a Spanish team press conference in the Olympic Village.
Both Nadal and Alcaraz will also compete in the singles at Roland Garros, where Nadal has won the French Open a record 14 times. Alcaraz captured the title in Paris for the first time last month.
"We trust in the great moment that Carlos is in," said Nadal. Alcaraz retained his Wimbledon crown 10 days ago, landing his fourth Grand Slam at the age of 21.
"We're going to give our all to try and at least leave with the peace of mind of having done everything possible," added Nadal.
Alcaraz said it was "a dream" to be able to make his Olympic debut in doubles alongside Nadal.
He too sounded a note of caution and insisted their star power was no guarantee of a medal.
"What I can say is that we're going to do give the best of ourselves... with great enthusiasm, let's hope we can enjoy it and play well," said Alcaraz, who beat Novak Djokovic again in this year's Wimbledon final.
Djokovic, who won singles bronze in 2008, will also be in Paris as the Olympic tennis tournament is held on clay for the first time since Barcelona in 1992.
