The 24-year-old Harry Potter star and Darke were all smiles as they posed for pictures at Radio City Music Hall in New York City.
Radcliffe and the Girls guest star went public with their relationship -- by letting themselves be seen holding hands on the streets of NY -- in late April after almost two years of dating.
The film actor turned Broadway star and Darke met on the 2012 set of Kill Your Darlings. The two reportedly had a brief fling and broke up before getting back together later that year.
Radcliffe currently lives in Manhattan and stars in the Broadway production of The Cripple of Inishmaan.