The 17-year-old was hit in the elbow. A second victim, a 20-year-old man, was hit in the lower back and buttocks.
The incident happened at about 6pm on Great Western Street in Moss Side yesterday. The man remains in hospital but his injury is not thought to be life-threatening.
Police have arrested a 26-year-old man and a 16-year-old boy outside the Greater Manchester area on suspicion of conspiracy to commit murder.
They remain in custody for questioning.
Superintendent Stuart Barton, of GMP’s Metropolitan Division, said: “Sunday was a hot day, and lots of people were on the streets of Moss Side enjoying the sunshine.
“A pleasant day was ruined when a girl and a man were shot in the street in what was a shocking incident. “We are doing all we can to find who is responsible for this attack.
“We have made two arrests so far, but the investigation is still very much ongoing and we’re following up a number of lines of inquiry.
“I’d like to appeal to anyone who saw anything at the time of the shooting and who has any information to call us.”
Anyone with information is asked to call Greater Manchester Police on 0161 856 2446 or the independent charity Crimestoppers, anonymously, on 0800 555 111.