The treat was tested in Austin restaurants last fall and "positive customer feedback confirmed the decision to launch the treat nationwide," Chick-fil-A said.
The drink combines the chain's vanilla IceDream, lemonade or diet lemonade and "a natural, sugar-free lime flavoring made from a blend of key limes, kaffir limes and Persian limes," it added.
A 16-ounce Frosted Key Lime starts at $3.25 and with diet lemonade has 280 calories and the regular has 350 calories.
Select locations have another seasonal item available through April 20 – a fish sandwich. It's not available every day and is not widely available nationwide.
It's one of the many fish specials that restaurants have leading up to Easter for lent.