In club football, Martins has won the Serie A title, the Italian Cup (twice), and the Italian Super Cup, all with Inter. With Birmingham he scored the winning goal in the 2011 Football League Cup Final. He has played European football with Inter, Newcastle and Wolfsburg, winning the UEFA Intertoto Cup with Newcastle. His highest scoring league seasons so far have seen him score 11 goals in the 2004–05 Serie A, and 17 in both the 2006–07 Premier League and 2014 MLS. In international football, Martins has been in the Nigerian squad for the Africa Cup of Nations in 2006, 2008 and 2010, and for the FIFA World Cup in 2010. He played for Seattle Sounders FC of Major League Soccer from 2013 to 2015, scoring 40 goals, before moving on to China.