Rooney had a disappointing 2011, knocked out in the semi-finals of the 400 metres at the World Championships in Daegu and finishing eighth as part of the British team in the 4 × 400 m relay. In 2012 Martyn started well, running 44.92s in April at the Mt. SAC Relays in Walnut, California, his fastest time since 2008. Rooney was unable to sustain that form going into his home Olympics, and he was eliminated in the semi-final of the 400 metres, running 45.31s. In the 4 × 400 metres relay final Martyn received the baton in sixth place and ran a blistering 44.1 second anchor leg, but was just unable to overtake Deon Lendore of Trinidad and so finished fourth.