The 16-year-old boy says he was attacked in the Falls Park area as he walked home in the early hours of Saturday morning.
The suspect is currently being questioned at the PACE custody suite in Musgrave PSNI station in Belfast.
He is being swabbed for DNA and his clothes are being forensically examined to see if there is a link between him and the rape attack.
The boy was able to return with police to the scene and show detectives where the attack took place.
The boy’s sister said a man followed her brother and shouted “come here, come here”.
She said the man then ran up behind him, and pulled him into bushes.
“He was crying his eyes out, he ended up managing to get away and ran home, and the man was shouting after him, he was in a terrible state,” the woman said.
“We phoned the police as soon as he came home and they came straight out. They didn’t leave us until 9am the next morning.
“They took his clothes, asked him all the questions, but because they didn’t know exactly where it had happened, he had to go back to the scene with the police, it was terrible.”
Sinn Féin councillor Janice Austin said she had been speaking to the police about the “very vicious attack”.
She appealed for anyone who could help police to catch the man responsible to come forward.