The robbery happened about 10:40 p.m. at 1923 Pulaski Highway (U.S. 40).
Two male robbers, one armed with a handgun, confronted a store clerk and he handed over cash from the register. The pair then ran east on U.S. 40.
The male clerk was not hurt, police said.
The gunman was described as 5-feet-5 to 5-feet-10 and 140-160 pounds. He was wearing black pants, a dark long-sleeved shirt and had a mask covering his face.
The other robber was 5-feet-5 to 5-feet-9 and 130-170 pounds. He was wearing a black sweatshirt and black sneakers and had a bandanna covering his face.
Anyone with information is asked to call troopers at 302-365-8566.
Tips also may be submitted anonymously through Delaware Crime Stoppers, which offers rewards, at 800-847-3333 or www.delaware.crimestoppersweb.com.