The armed suspect walked into Kay's Liquor on Belmont and Fifth around 8:30 Tuesday evening.
Police say he had a rifle and ordered the clerk to give him money from the register.
The victim complied and gave him an unknown amount of cash.
The suspect walked out of the business and took off in a dark colored pickup truck.
Investigators say the suspect was wearing an LA Rams sweater and sweatpants.
Anyone with information is asked to call Fresno Police.