The 23-year-old forward completed a move to UD Levante on a five-year deal which could see him in Spain until 2023.
Premier League side Liverpool indicated interest in the forward before the start of the 2018 FIFA World Cup.
An injury in the Super Eagles preparation camp prevented the forward from the final list to the World Cup.
Moses move comes after KAA Gent also let go of Nigerian forward Samuel Kalu who left to French outfit Bordeaux.
The Nigerian forward previously played for AS Trencin in Slovakia before his move to KAA Gent in Belgium.
A statement on the official website confirmed the arrival of Moses at Levante.
The statement reads, "Moses Simon will defend the Barça shirt during the next five seasons following the resolution of the agreement reached between Levante UD and KAA Gent."
In his time at KAA Gent, Moses scored 21 goals in a total of 108 appearances and at Trencin he scored 13 goals in 33 games for the Slovakian side.
Moses who welcomed a daughter with his wifeis expected to be called up for the Super Eagles next African Cup of Nations (AFCON) qualifier against Seychelles in September.