The incident, which occurred in Barry yesterday evening, left a 17-year-old boy injured.
He was taken to hospital for treatment, but police have confirmed his injuries are not life-threatening or life-changing.
A spokesperson for South Wales Police said: “We can confirm that an 18-year-old man has been arrested in connection with the stabbing which occurred in Barry earlier this evening and he is in police custody.
“The 17-year-old male victim required hospital treatment but his injury is not life changing or life threatening”.
Police confirmed that a suspect had been arrested and that they weren’t looking for anybody else at this stage.
Detective Superintendent Lisa Gore said: “We have arrested a suspect and at this stage we are not looking for anybody else.
“We understand this has caused significant concern and we will have an increased presence in the area over the coming days to reassure people.
“I would like to thank those who have assisted our investigation so far.”
Earlier in the evening, South Wales Police launched an investigation and enquiries to find the suspect were ongoing.
Police urged anyone who may have witnessed the incident to get in touch with them.
Detective Superintendent Lisa Gore said: “Incidents such as this one are extremely rare and we understand how distressing this incident was for those in the area at the time.
“We have launched an investigation and a team of officers are carrying out arrest enquiries for the suspect.
“We have further increased the police presence in the area and this will continue over the coming days”.
