It happened around 3:10 a.m. on March 10 aboard a northbound 2 train as it pulled into the 238th Street / Nereid Avenue station in the Bronx.
The NYPD released surveillance photos and video of the suspect Friday.
Police said he repeatedly punched and kicked the victim in the head and body.
She was treated at the 241st Street station for cuts and swelling to her face.
On Saturday afternoon, police said the suspect had been apprehended and was in custody.
The victim was treated and released is now getting help from officials, Shea wrote on Twitter.
“Thank you to the worldwide community for the tremendous assistance,” Shea wrote.
More details were expected to be released.