Ciaran O’Leary is a professional poker player, who grew up in the single street village of Carrigaline, County Cork, Ireland. Ciaran O’Leary was one of three children born to greyhound trainer Terry O'Leary and his wife Sheila. During his childhood, Ciaran O’Leary spent his time going with his father to the "Point to Point" Horse track, the Cork Greyhound track, and to various betting shops across County Cork. He would very often be found in the corner observing the different poker games that were going on. He started playing poker when he was 8, and he preferred to play poker with lads elder to him, because it involved more money. Ciaran O’Leary married Dana Langworthy, a legal recruiter, on November 24, 2001 in San Francisco. The couple moved to Seattle in 2005, and they have two sons, Aidan and Liam.
In 1997, Ciaran O’Leary moved to the United States with just $1,000 in his pocket. On his day of arrival, he played his first poker game at the Boston club and won $3,000 in less than two hours. Then he traveled to reach San Francisco, where he quickly made his presence felt in the Bay Area poker scene. He was frequently visiting the Lucky Chances casino, and it was there that Ciaran O’Leary was nicknamed "Big C" because his name was constantly being mispronounced.
Ciaran O’Leary has also won tournaments in Colorado, Washington, and Nevada. At the World Poker Challenge/World Poker Tour (WPT) Season 4 held on March 25, 2006, Ciaran O’Leary finished 12th to take home $4, 804 in Event 33 No-Limit Hold'em. In the Green Joker Poker Festival of Poker II: No-Limit Hold'em held on May 27, 2007, he ranked second and won prize money of $4,025. He would always cherish June 2nd for ranking first in Event 3 – No-Limit Hold'em at the 38th Annual World Series of Poker (WSOP) held on the day and went home with $727,012. On the very next day, the Irish Classic No-Limit Hold'em was held, in which he ranked 2nd and walked away with $5,242. On Jan 4, 2008, he took part in the No-Limit Hold'em event at the PartyPoker Irish Poker Championship and took home $7,864 after finishing 13th. The same year, on February 1st, when the Friday No-Limit Tournament was held, Ciaran O’Leary secured 2nd place in the No-Limit Hold'em event and won $12,190 in prize money.
Ciaran O’Leary, whose ambition is to be the best player, says his favorite game is Five Card Draw Poker Jacks or better. He claims that he would like to change the payout structure in a poker tournament when one finishes on the bubble. He has a diverse range of hobbies like pool, golf, writing, poetry, and listening to music. He also likes to watch Seattle Seahawks football team and San Francisco Giants baseball team when they are playing. Ciaran O’Leary has a great respect for Chris Ferguson, Barry Greenstein, Daniel Negreanu, and Dan Harrington, who are among the best players in the poker world.