Acting Senior Sergeant Jennifer Hansen said police were praising a "vigilant member of the public" for their assistance in the arrest.
Locals were more aware of poachers due to previous incidents in the area, she said.
"This time the caller also attained a registration, which is great and certainly made things easier for us.
"There are times when members of the public are unsure whether or not to call us.
"In this instance, not only has an offence been committed, but this is a safety issue and affects business for farms in the area.
"We absolutely want to be made aware so we can target those responsible and prevent further offending."
The man has been bailed to appear in the Masterton District Court on Monday, August 6, on charges of possession of a firearm without a licence, poaching and possession of cannabis.