MBS, which previously worked with Ogilvy & Mather Singapore on its creative account, was reportedly on the lookout for other creative partners earlier this year in April.
The integrated resort was thought to be in favour of working with more boutique-like agencies at the time.
TBWA will now take on work for MBS' casino while Formul8 has been tasked with its hotel, MICE, Sands SkyPark as well as its food and beverage business.
Razorfish has also been tasked to take on work for the IR's shopping mall - Marina Bay Sands Shoppes.
In May, the Las Vegas Sands Corp project handed its estimated US$15 million media planning and buying business to Starcom in the city-state following a three-way closed-door pitch process.
The $5.5 billion resort will celebrate its official grand opening this week.