Marketing first announced plans to develop the partnership between the two company's in September, and the first rollout starts today (29 March).
Four Boots stores in Canary Wharf, Swansea, Abingdon and Milton Keynes now stock a selection of Waitrose lunchtime products, such as sandwiches, wraps and desserts, as well as items from the Boots Shapers range.
The second trial will start next month with three Boots stores, yet to be disclosed, stocking a larger range of lunchtime and convenience food.
It is not known how long the promotions will run, but the sales performances will be monitored closely by both retailers.
The move enables Boots customers to buy groceries, including products from the Essential Waitrose range, and ‘special treats' from a range of 1,500 products supplied by the supermarket.
For Waitrose, the trial is part of plans to dramatically increase its UK presence. In September, it announced plans to open 300 convenience stores and stated there were 6.5 million shoppers without easy access to a Waitrose store
As part of the trail, Boots health and beauty products and toiletries will be on offer within seven Waitrose stores.
These include Bristol Westbury Park, Dorchester, Ringwood, Bury St Edmonds and Hersham, which will stock the products from April and May. Products will include items from the No7 skincare and cosmetics brand.
Two of the trial store locations will also include a full Boots pharmacy offer, but the locations have yet to be announced.
The trial builds upon the growing relationship between both retailers. Last year the re-branding of Boots UK-owned pharmacies to 'Boots Pharmacy', located in 13 Waitrose stores, was completed.