The man was charged after more than 40 children were taken from the community amid allegations that some adults were disciplining them with objects such as straps and whips.
The identities of the children are protected under a publication ban and The Canadian Press is not naming any of the accused or the small community where they live.
In court today, one man pleaded guilty to six counts, including assault and assault with a weapon, dating as far back as 2010.
Court was told the weapons included a leather strap and an iron poker.
No date has been set for the man's sentencing.
Thirteen people from the community were originally accused in the case, but the Crown later dropped charges against all but four, some of whom remain before the courts.
Child welfare officials started returning children to their parents last year, after the parents agreed to follow guidelines for disciplining children.
Old-order Mennonites typically shun modern conveniences, including electricity and cars, and adhere strictly to Biblical teachings. While most believe in corporal punishment, those who know the community have said they are inherently non-violent.