The 20-year-old will join the Barcelona B team for the moment, the LaLiga champions said in a statement.
"The 20-year-old striker, named J-League's Young Player of the Year in 2018, joins from Kashima Antlers on a four-year deal," the Catalan club posted on its official Twitter handle.
The Spanish team said that it had paid 1.1 million euro to contract Abe, who has made three appearances for the Japanese national team, Efe news reported.
Abe's Barcelona B contract will include a 40 million euro buyout clause, which will be increased to 100 million euro when he becomes a first team player.
Barcelona's announcement came a few days after the Japanese club had revealed a basic agreement with the Spanish powerhouse to transfer the player, who made his debut with the national team against Chile in the recent Copa America.
He joined Kashima in 2017 straight from high school.
Having already dipped his toe in the water playing for the national team, which featured as a guest in the Copa America, Abe looks almost certain to land a more crucial role for the Samurai Blue in the Tokyo 2020 Olympic Games.
Kashima Antlers are currently fourth in J-League. So far this year, Abe has played in 14 matches, scoring one goal.
Barcelona won its 26th league title in 2018/19 but failed to add more to its silverware, missing out on the Copa del Rey with a 1-2 loss to Valencia in the final and tumbling out of the Champions League in a dramatic fashion, succumbing to Liverpool 0-4 in a semifinal second leg, losing its 3-0 advantage from the first bout.
( With inputs from IANS )