The 600sq m shop in Trinity Square, Nottingham, is the first of four trail-blazers of the branch trial, said managing director Mark Price.
Unlike other convenience stores, there was a big focus on specialist service counters and fresh produce, he said.
This included counters for salads, cheeses, fresh meat and fish. The Trinity Square store is the 198th Waitrose to open.
"We want to revive that traditional sense of service typical of convenience shops, which customers value, but within a fresh and contemporary setting," he said.
Waitrose confirmed it would open a second convenience shop in Bristol in the spring, and two more trials were expected at undisclosed locations.
"You shouldn't have to compromise the standard of your shopping experience just because a store is smaller and designed for convenience."