"The owner was injured and taken to Whanganui Hospital where he was treated and discharged."
The two offenders fled the scene in a stolen vehicle which has since been recovered.
Police made inquiries in the area, and were speaking with the shop owner and witnesses, conducting a scene examination and reviewing CCTV footage.
The shop owner is being supported by Victim Support services.
Police would like to hear from anyone who may have been in the Springvale area around that time on Sunday night and seen anything suspicious.
They are seeking sightings of a white 1993 Toyota Corolla and a small silver car that was seen being overtaken by the Toyota immediately after the robbery.
People who may have information should contact Whanganui Police on 06 349 0600, or they can call Crimestoppers anonymously on 0800 555111.
It is the fourth such robbery in Whanganui in the past six months and so far no arrests have been made.
Other robberies in Whanganui during past six months
April 27, 2017: Four offenders entered the McDonald's restaurant on Liffiton Street and demanded money before fleeing across State Highway 3 towards land near the Gateway Motel where they got into a car.
*December 13, 2016: Four armed offenders entered the BP Connect service station on London Street about 3.30am and made off with cigarettes.
*December 11, 2016: Three offenders took alcohol and cash as well as cigarettes from the liquor store in Purnell Street.
Police say investigations in all the above robberies are ongoing.