The transatlantic migration of nearly two million Irish following the Irish Potato Famine (1845–1849) finally brought the holiday to America. Scottish emigration from the British Isles, primarily to Canada before 1870 and to the United States thereafter, brought the Scottish version of the holiday to each country.

Scottish-American and Irish-American societies held dinners and balls that celebrated their heritages. 

Home parties would center around children's activities, such as bobbing for apples, and various divination games often concerning future romance. Not surprisingly, pranks and mischief were common as well.

Halloween originated under the name of Samhain as a Pagan festival among the Celts of Ireland and Great Britain. Irish and Scottish immigrants carried versions of the tradition to North America in the nineteenth century. Other western countries have embraced the holiday as a part of American pop culture in the late twentieth century.

Halloween is now celebrated in parts of the western world, most commonly in Ireland, the United States, Canada, Puerto Rico, the United Kingdom and sometimes in Australia and New Zealand. In recent years, the holiday has also been celebrated in parts of Western Europe.

Halloween is very popular in Ireland, where it is said to have originated, and is known in Irish as "Oíche Shamhna" or "Samhain Night". Pre-Christian Celts had an autumn festival, Samhain, "End of Summer", a pastoral and agricultural "fire festival" or feast, when the dead revisited the mortal world, and large communal bonfires would hence be lit to ward off evil spirits.

On Halloween night in present-day Ireland, adults and children dress up as creatures from the underworld (e.g., ghosts, ghouls, zombies, witches and goblins), light bonfires, and enjoy spectacular fireworks displays (despite the fact that such displays are usually illegal). The children knock on the neighbors' doors, in order to gather fruit, nuts, and sweets for the Halloween festival. Salt was once sprinkled in the hair of the children to protect against evil spirits.

The houses are frequently adorned with pumpkins or turnips carved into scary faces; lights or candles are sometimes placed inside the carvings to provide an eerie effect. The traditional Halloween cake in Ireland is the barmbrack, which is a fruit bread. Each family member gets one slice. There is a piece of rag, a coin or a ring in each cake; if one gets the rag, then financial prospects are doubtful. Getting a coin indicates a prosperous future, and getting a ring is a sure sign of impending romance or continued happiness.

Games are often played, such as bobbing for apples, where apples, peanuts and other nuts and fruit and some small coins are placed in a basin of water. The apples and nuts float, but the coins, which sink, are harder to catch. Everyone takes turns catching as many items possible using only their mouths. In some households, the coins are embedded in the fruit for the children to "earn" as they catch each apple. The Scottish and English have adapted the tradition to a game named "ducking", in which a participant quickly dunks in a water-filled container in an attempt to get a prize, without being submerged too long. Another common game involves the hands-free eating of an apple hung on a string attached to the ceiling.

Irish children have a week-long Halloween break from school; the last Monday in October is a public holiday given for Halloween even though they often do not fall on the same day