He was released bail of 300-birr (around 31-dollars, 21-euros) on Wednesday.
RSF urged Ethiopian government to “amend the newly-adopted media law in order to eliminate prison sentences for press offences”.
Aregawi’s private Amharic language weekly Reporter published an article last month citing two former employees of the brewery as saying they were wrongfully dismissed.
The brewery company had sued the paper for libel.
Ethiopia was only removed from RSF’s blacklist of media offenders in May, having been labelled “an enemy of the Internet” along with Zimbabwe