The world champions ran riot against their rank no. 12 visitors, solidifying top spot in League A Group 3 with two wins from two matches following a thrilling 3-2 victory over England at Wembley last weekend.
The 2025 Ballon d'Or runner-up was directly involved in each of Spain's first three goals of the match before being substituted out of the match for Victor Munoz in the 68th minute.
Yamal's exit would have been a relief for Croatian left-back Josko Gvardiol, who was terrorised by his opponent for more than an hour, being dribbled past by Yamal at least once as the Spaniard made good use of Spain's 64% of possession before half-time.
The 19-year-old was Flashscore's player of the match with a rating of 8.7 out of 10 for his two goals and assist, the first time in his 35 national team appearances that he registered three goals or assists in a single match.
After the team celebrated their World Cup victory by lifting the trophy in front of a packed Ramon Sanchez-Pizjuan Stadium, it didn't take long for the players to continue the party on the pitch.
Yamal scored in the second minute of a match for the second time in four days - this time opening the scoring after 70 seconds, having done so just 105 seconds after kick-off at Wembley.
Coupled with eight goals and six assists in just eight La Liga or Champions League matches for Barcelona, Yamal's explosive performances have seen him surge into favouritism ahead of England's Harry Kane to go one better and win the Ballon d'Or in four weeks' time.
That would see him eclipse the great Ronaldo Nazario and become the youngest winner of football's greatest individual honour.
Spain manager Luis de la Fuente said he was "delighted" with Yamal's two performances against England and Croatia, hailing the cross to set up Marc Pubill's header from near the penalty spot as just as good as either of his two strikes.
"I don't like to focus too much on individual performances, but sometimes it's impossible not to do so," de la Fuente said of Yamal.
"Lamine wants to show the world the kind of player he is.
"Today we enjoyed his magic again, but he puts his magic at the service of the team.
"That says a lot about the player. In the future he'll be even more well known for what he does in his collective play.
"We're lucky to have him with us. Within the group, he's very loved."
Spain continue their pursuit of their second UEFA Nations League title at home to Czech Republic in Oviedo on Saturday before visiting Croatia next Tuesday night.