The Metropolitan police constables Kevin Hughes, 36, and David Hair, 42, were both found not guilty of a count each of using threatening words or behaviour to cause alarm and distress and one count each of racially aggravated harassment at Westminster magistrates court in London.
Hughes, of Brentwood, Essex, admitted saying a black man looked like a monkey but said it had nothing to do with his race and he was pointing him out during a discussion about evolution, the court heard.
He was also accused of saying black people were "more closely related to Neanderthals" but said he did not know what the word meant.
Hughes said he made the comments because he saw a black man with "elongated arms" and a gait like a monkey while out on patrol with three colleagues in Newham, east London, on 22 February.
The officer, who allegedly said black people had not evolved and "lived in mud huts in Africa", told the court it was "upsetting" that anyone would think he was racist.