It happened at 11:15 a.m. Friday in the parking of the The Well, a store on Lancaster Pike in Hockessin.
Police say a 2000 Dodge Ram pickup truck driven by Loren Salfrank, 62, of Wilmington suddenly accelerated, slamming into the back of a cargo trailer parked at the store's loading dock.
The pickup truck traveled several feet under the trailer, trapping Salfrank and his passenger, 29-year-old Andrew Hoover of Wilmington.
Quick-thinking store employees attached a tow rope to the back of the pickup truck and used another vehicle to pull it out from underneath the trailer rig.
They administered first aid to both men until medics arrived.
Both men were taken to Christiana Hospital Trauma Center, Salfrank by ambulance, Hoover by helicopter.
Both were listed in stable condition with injuries not believed to be life-threatening.
Investigators are working to determine what caused the pickup to accelerate, hitting the trailer rig.
No one else was injured.