The NFL superstar, 26, accompanied his longtime girlfriend to the NCAA match between Baylor and Texas Tech Red Raiders on Wednesday.
But it was events off the court which got tongues wagging, despite the home team extending their impressive season record to 20-6.
The Chiefs quarterback – who led his team to the Super Bowl in 2020 – spent three years at Texas Tech, throwing for 11,252 yards and 93 touchdowns
And he was given a heroes welcome by the crowd ahead of the much-awaited showdown in Lubbock.
The exchange quickly went viral, with a number of users asking if anyone could read lips to decipher the conversation.
But the overwhelmingly negative tone clearly had an affect on Mahomes, who leap to the defence of his fiancée this morning.
He tweeted: “Man people are weird…love you babe”.
Brittany has been the target of slurs online in the past and was recently criticised over a video which showed her spraying freezing Kansas City fans with champagne.
After that incident, she wrote on Twitter: “I just wish I could do what I want without getting attacked every week.”
And in recent weeks Matthews revealed on Instagram she is selling t-shirts to benefit a local anti-bullying charity.
High-school sweethearts Mahomes and Matthews got engaged in September 2021 and both a date and venue have been sorted for their wedding this year.
The pair have an 11-month old daughter named Sterling, with Mahomes revealing on Tuesday how had showered the pair with gifts for Valentine’s Day.