The license approval for its casino brand strengthens William Hill’s presence in Spain, across the sports betting and online market, with the operator stating Mr Green’s launch will support its multi-brand strategy.
The operator acquired Mr Green in a deal worth £245m ($318.4m) in January 2019 from its parent company MRG.
William Hill International managing director and MR Green CEO Patrick Jonker, said: "This is an important milestone within our strategy.
“With the combination of two industry leading brands, we look forward to deliver the best player experience within sports and gaming."
The launch comes less than a month after it was announced that an agreement had been reached for Caesars Entertainment to acquire William Hill for approximately £2.9bn, expected to be competed in the second half of 2021.
While in August, William Hill reported a 32% year-on-year revenue fall for H1 2020, down to £554.4m, as a result of coronavirus pandemic impact on retail activities, which saw the operator close 119 betting shops permanently.