It says its Unicorn Frappuccino - a brightly-coloured confection of ice, mango syrup, "creme" and "sour blue drizzle" - changes colour when mixed.
Some social media users said they wanted to try the drink, while others didn't seem so keen.
And there were queries on Twitter about the food dyes used in the drink.
"Unicorn food" is an internet craze that features pictures of and recipes for brightly-coloured food in pastel and rainbow hues, which supposedly represent colours found on the mythical creatures.
"Unicorn toast" - toast with bright spreads - is an example.
Some of the food is coloured with naturally highly-coloured ingredients such as beetroot and turmeric, while some relies on artificial food colouring.
Corinna Becker of the Autism Women's Network asked Starbucks Canada: "Could you tell me whether the food dyes in the unicorn frappucino are natural or artificial? Cause red = migraine for me."
Starbucks said the drink consisted of "a sweet dusting of pink powder, blended into a creme Frappuccino with mango syrup and layered with a pleasantly sour blue drizzle. It is finished with vanilla whipped cream and a sprinkle of sweet pink and sour blue powder topping."
Twitter user Dragoneer said: "My god. @Starbucks has a UNICORN FRAPPUCINO? This is so freakin' amazing I do not have words to describe its sheer majesty."
Another, Mair wrote: "Gutted that the Starbucks unicorn frappucino is a US only thing, they look so cool :ccccc."
But some Twitter users were a little more scathing about the concoction. Baillie Starnes tweeted: "If you care anything at all about your health, sugar intake, or the life of a barista, do not order this."
According to CNN Money, a "tall" Unicorn Frappuccino with whole milk has 280 calories, 11 grammes of fat, and 39 grammes of sugar.
That's more calories than a typical jam doughnut, or three dark chocolate digestive biscuits.
The coffee giant plans to sell the drinks in the US, Mexico and Canada between 19 April and 23 April.