The 35-year-old Brazilian attacking midfielder arrived at Genoa in the summer of 2023 and has made 58 appearances across all competitions for the club, contributing six goals and two assists.
Messias used the announcement to express his affection for the club and its supporters.
"I thank the club, the whole staff, my teammates and the fans for their esteem and affection," he said. "It is a privilege for me to wear the Genoa shirt, to be part of this group and to play in a stadium and for supporters like these.
"I can't wait for the new season to begin."
Chief of football Diego Lopez paid tribute to the Brazilian's contribution and outlined what the club expects from him going forward.
"Junior is a player with excellent technique, a fans' favourite and an important presence for the team's balance," Lopez said. "We are happy to be able to count on his experience. He has often been decisive with his play — we expect a great contribution from him given his quality."
The renewal keeps an experienced and popular figure at the Marassi ahead of a new Serie A campaign, with Genoa leaning on Messias' technical quality and leadership as they look to build on their recent seasons in the top flight.
For a player who came through the lower tiers of Brazilian and Italian football before establishing himself in Serie A, Messias' continued presence at Genoa represents both personal loyalty and a recognition that the right conditions exist for him to remain an effective contributor at the top level.
His renewal hands Genoa a reliable attacking option heading into a new campaign, with the club confident he can deliver the kind of decisive moments that have made him a popular figure among the Genoa faithful since his arrival.