Solomona, 22, joined the Tigers from London Broncos along with team-mates Scott Moore and Mike McMeeken and ended the season with 18 tries in 15 games.
The former Melbourne Storm flier spent part of the 2015 Super League season out with ankle and knee injuries.
"Everyone has made me feel at home here and we have a great team," Solomona told the club website.
Head coach Daryl Powell added: "Denny can become the best winger in Super League if he continues the hard work and application he has shown so far.
"He is a natural finisher with speed to burn. I'm looking forward to helping him achieve his huge potential over the next three years."
Castleford winger Denny Solomona has signed a new deal that will expire at the end of the 2018 season.