The 21-year-old finished second the T47 100m in a time of 11.30 seconds, which was just 0.06 seconds of his lifetime best.
Arnott, a T46 athlete, was only beaten on the Gold Coast by T47 Nigerian Suwaibidu Galadima, who clocked a fast 11.04 seconds. Jamaica’s Tevaughn Thomas took third in 11.63 seconds.
Afterwards Arnott said: “It was a surreal experience with all the crowd cheering. It was an amazing feeling. I think I’ve done my country proud.”
He added: “I didn’t know anyone going into the race. I couldn’t worry about other people – it was about my lane.
“We both came out and gave our best performance and he (Galadima) came out on top.”
Arnott, who was part of the England athletics team with club colleague David King, was the third Plymothian to win a medal on Friday at the Gold Coast. He followed in the footsteps of Tom Daley and Matthew Dixon, who made the podium in the 10m synchro event.
Daley took gold with former Plymouth diver Dan Goodfellow, while Dixon claimed silver with Noah Williams.