The 31-year-old makes the switch from Seattle Sounders, where he scored 43 goals in 84 appearances for the MLS club he joined in March 2013.
Martins was linked with a move back to the Premier League in the January window, but British agent Tony Harris along with the player’s attorney Soroosh Abdi brokered the deal taking the Super Eagle to China instead.
Martins, who joins Senegalese striker Demba Ba at the Shanghai club,becomes the latest high-profile player to make the switch to the cash-rich Super League.
Colombia striker Jackson Martinez, former Chelsea midfielder Ramires, Cameroon captain Stephane Mbia and ex-Serie A duo Gervinho and Fredy Guarin are among the other big Chinese signings in 2016.
Martins burst into the international limelight at Italian side Inter Milan before switching to Newcastle in August 2006. He scored 35 goals in his three seasons with the Magpies.
The striker, who has also had spells in Germany, Russia and Spain, will be remembered for scoring Birmingham City’s winner in their 2-1 Carling Cup final victory over Arsenal in 2011 – the club’s first silverware since 1963.
He has scored 18 goals in 41 international appearances for three-time African champions Nigeria and was voted Africa’s most promising talent in 2003 and 2004.