The former head of the New York City government watchdog Citizens Union allegedly attacked a man with a hammer the day after Thanksgiving, police said.

Ex-executive director Dick Dadey, 62, was arrested Thursday evening and charged with assault over the domestic incident outside 785 Belmont Ave. in East New York, according to cops.

Dadey allegedly hit a 37-year-old man with a hammer in the thigh and foot multiple times, police said.

The victim was taken to Lenox Hill Hospital and was expected to recover, according to police.

Dadey was expected to appear in court later Friday.

The activist went on a leave of absence from the good-government group in 2017 after being busted with meth and ecstasy.

His LinkedIn page says he is currently self-employed as a nonprofit consultant.