A 39-year-old from Manchester faces charges of sexual touching without consent and trespassing with the intention of committing a sexual offence.
The alleged incident happened at Cathays Terrace on 22 September and was the second of three over five days but none of them are linked.
The man has been remanded in custody.
He will appear via video link before Manchester and Salford Magistrates Court on 5 January.
Police investigating a series of sexual assaults in Cardiff in September have charged a third man.