The one-time Spain international arrives at the Stadio Picchi in a deal worth £470,000 and will spearhead a new-look strike force following the departure of Cristiano Lucarelli.
He joins Francesco Tavano in the Granata attack after the Valencia hitman also made a move from Spain to Italy.
Tristan has been without a club since January when he was released by Mallorca after having failed to make an impression following his move from Deportivo La Coruna.
Despite having netted 77 goals in 179 appearances for Depor, the 31-year-old could muster just a solitary strike in 13 appearances for Mallorca during his six-month spell on the island.
That form, along with questions over his attitude and fitness, led to his release at the turn of this year.
But Livorno were willing to take a risk on him and will be hoping he can recapture his form of the 2001-2002 season when he finished top scorer in La Liga.
Tristan will now join his new team-mates at their pre-season training camp where he will undergo a medical.