The man arrested and charged over the wounding of a nine-year-old Timaru schoolboy has appeared in court and will be kept in custody while his mental state is assessed.

The 26-year-old appeared in Timaru District Court on Wednesday, nearly one week after the Oceanview School pupil was found distressed and with facial injuries, about 15km from his school and 45 minutes after classes finished.

Police arrested the man on Tuesday night and charged him with injuring the boy with intent to commit grievous bodily harm.

He was granted name suppression and remanded in custody for a psychiatric assessment until his next appearance next month, Radio New Zealand reports.

Earlier, Mid Canterbury area commander Inspector Dave Gaskin said the man and the boy were not strangers.

The arrest was made after information from the community.

"A number of people saw different things which, although they didn't mean much to them at the time, by the time we pieced it all together we managed to put a pretty good case as to what had happened."