The theft and assault were reported about 7:40 a.m. Sunday at the CVS Pharmacy store at 16th and South streets.
Police say the man grabbed a prepaid cellphone and ran out of the store. The clerk chased the man and tried to restrain him in the parking lot, but the man used a pair of scissors to stab the clerk in an elbow. Officers soon spotted the man and arrested him.
The clerk refused medical attention.