The Portuguese veteran was strongly linked with a return to his homeland, but has instead decided to continue playing abroad after spending a decade in England
The Portugal international became a free player last week after West Ham decided to terminate his contract, bringing an end to a four-year association.
Boa Morte, who has signed a two-year contract with Larissa, took part in the club's training session on Monday morning already and will be officially unveiled on Tuesday.
The 34-year-old joins Larissa together with Brazilian midfielder Cesinha, who arrives from Dinamo Bucharest after four years in Romania.
Boa Morte, who began his career abroad in 1997 with Arsenal, had spells at Southampton and Fulham before signing for West Ham in 2007.