They join Montenegro and Greece on the planes to Japan for the Games in 2021, after finishing in the top three at the Olympic Qualifying tournament in Rotterdam
Croatia sealed their spot with a 25-24 penalty victory over Russia on Sunday (21st February).
Dramatic win on penalties for Croatia
Croatia and Russia knew that the winner of their bronze medal match would seal the final Tokyo Olympic ticket.
The Russians undoubtedly had a psychological advantage going into the must-win match, having beaten Croatia 14-13 earlier in the tournament to top Group B.
But Croatia avenged that defeat in the most thrilling way possible, with a 25-24 penalty victory.
After 13 penalties for each team, Croatia's Josip Vrlic stepped up to slam the winning shot home, and start the celebrations for his teammates.
The victory means that team veteran Maro Jokovic, who helped Croatia land Olympic gold at London 2012, will have the opportunity to land a third Olympic medal at Tokyo 2020.
After topping Group A, Montenegro were the first team to book their place in Japan, when they edged Croatia 4-2 in the semi-finals on Saturday (20 February).
Later that day, Group A runners up Greece snapped up the second Olympic qualifying berth with a 13-10 semi-final victory over Russia.
In the final between the two qualifiers, Montenegro ran out 10-9 winners to maintain their unbeaten tournament record.
The 12 teams who will compete for Olympic gold in men’s water polo at Tokyo 2020 are hosts Japan, World League winners Serbia, World Championships qualifiers Italy and Spain, continental champs USA, Australia, South Africa, Hungary and Kazakhstan, in addition to World qualifiers Montenegro, Greece, and Croatia.