It happened around 8:45 p.m. on West 42nd Street near Ninth Avenue.
Police said two women were walking when they were approached by the suspect, who told them to take off their masks and then struck one of the women with a hammer.
The 31-year-old victim was hospitalized with a cut to her head, but is expected to be OK.
The NYPD Hate Crimes Task Force is investigating the attack as a possible bias crime.
Anyone with any information is asked to call the NYPD’s Crime Stoppers hotline at 1-800-577-TIPS (8477), or for Spanish, 1-888-57-PISTA (74782). You can also submit a tip via their website or via DM on Twitter, @NYPDTips. All calls are kept confidential.