The first was at 9.45am at a Liquorland store on Liberator Drive, Paralowie.
A man armed with a knife stole cash from the till and rode off on a bike and was last seen towards Bolivar Road.
The offender is described as Caucasian, 35 years, 5’3″ and wearing a grey hooded top and dark tracksuit pants with stripes.
He had red hair and a red goatee style beard.
He wore a white foam bike helmet with a baseball cap underneath and was carrying a purple Coles bag.
The second robbery was at a post office on Whites Road, Salisbury at 9.58am.
A man armed with a knife threatened staff before stealing cash.
The offender was wearing a black hooded top, black tracksuit pants and a bandana or cloth covering his face.
He left on foot with a black back pack and was last seen on Bingham Street.