Whiskey v Bourbon, What’s The Difference?

Whiskey is a distilled spirit made from fermented grain mash and matured in wooden casks—but the real story is in the details. Among global styles, Irish whiskey is celebrated for its smooth, layered character, often crafted from a mix of malted and unmalted barley and triple-distilled for exceptional purity. 

To craft Jameson whiskey, for example—we blend pot still and grain whiskey, then mature the spirit in a combination of ex-bourbon barrels and seasoned sherry casks, creating a whiskey that’s as versatile as it is rich.

By law, for a spirit to be considered Irish whiskey, it must meet these key criteria:

• Distilled and matured on the island of Ireland
• Made from a mash of cereal grains (commonly including both malted and unmalted barley)
• Distilled to no more than 94.8% ABV
• Matured in wooden casks for at least three years
• No additives allowed except water and plain caramel colouring

For more on whiskey basics, see our whiskey guide for beginners.

What Is Bourbon?

In contrast, bourbon is America’s sweeter cousin—made primarily from corn and aged in brand-new, charred oak barrels. 

Bourbon also comes with strict rules. To carry the name, it must:

• Be made from at least 51% corn
• Be distilled without additives
• Age in brand-new, charred oak barrels
• Mature at least two years to be called “straight bourbon”

Thanks to the high corn content, bourbon tends to be sweet and bold, with dominant notes of vanilla, caramel, and spice.

The Grains of Distinction: Irish Whiskey vs Bourbon

• Irish Whiskey → Barley is the hero, often a mix of malted and unmalted barley, giving a spicy, creamy character.
• Bourbon → Corn-heavy mash bill (minimum 51%), balanced with rye, wheat, or malted barley.

At Jameson, our triple-distilled blended Irish whiskey uses both pot still and grain whiskey, matured in a mix of ex-bourbon barrels and seasoned sherry butts. That’s how we achieve our signature smoothness, a true grain-to-glass handshake between Ireland and America.

If you’re curious how Irish whiskey compares to other spirits, check out our guides that compare whiskey vs brandy and rum, or our one that covers all the main whiskey types and flavours. 

Battle of the Barrels: Ageing Matters

Oak is the backbone of both whiskey and  bourbon maturation. But here’s the catch:

• Irish Whiskey: We happily give those bourbon barrels a second life, alongside seasoned sherry butts. Together, they impart toasted wood, vanilla, and sweet dried fruit notes into Jameson.
• Bourbon: By law, aged only in new, charred oak barrels. Those casks can be used once, then often shipped abroad.

Fun fact: There are more bourbon barrels in Kentucky than there are people. In Midleton, we’ve got nearly four times as many barrels maturing as there are people in all of County Cork.

Where They’re Made: Ireland vs Kentucky

• Irish Whiskey: To carry the “Irish” name, whiskey must be matured for at least three years on the island of Ireland (no matter the type of Irish whiskey)
• Bourbon: Must be made in the U.S. Congress even crowned it “America’s Native Spirit” in 1964. Kentucky remains the bourbon capital, producing about 95% of the world’s supply.

Irish whiskey may be a globetrotter, but bourbon is proudly American at heart.

To see how Irish whiskey compares with its Scottish cousin, visit our Irish whiskey vs Scotch guide.

Whiskey vs Bourbon: Flavour Profiles

• Irish Whiskey: Known for smoothness, subtlety, and versatility. Jameson is approachable neat, over ice, or in cocktails – mellow yet complex.
• Bourbon: Sweet and bold, with notes of vanilla, oak, caramel, and spice. Rich, but less subtle than Irish whiskey’s delicate balance.

Think of Irish whiskey as the smooth operator, and bourbon as the sweet charmer.