Under the three-year deal, Switzerland firm Alponics will supply Sativa with CBD distillate and isolate until the end of 2022.
Alponics, which was founded by Pacific Rim Plantation Services last year and has operations in Vaud and Valais, is expected to begin production this autumn.
"This commercial agreement with Alponics further advances our smart-sourcing strategy,” said Sativa founder and chief executive, Geremy Thomas.
"We look forward to a long and mutually beneficial relationship with Alan Chaytor and his impressive team."
Last month Sativa decided to abandon a plan to grow its own cannabis produce at a 7.5-acre Wiltshire site.
The company decided sourcing raw material would provide greater returns than growing its own supply.
As part of the new strategy, Sativa announced in late May that it had signed a commercial offtake agreement with Portuguese cannabis oil supplier, MeridianTulip – Empresa Medicinal Lda.
Sativa will acquire low tetrahydrocannabinol (THC) cannabis oil for the UK manufacturer of CBD products at its Somerset headquarters.
THC is a compound in the cannabis plant that gives the “high” associated with recreational use while CBD is non-psychoactive. Medicinal cannabis, which was legalised in the UK late last year, contains CBD and low levels of THC.