Cricket Ireland, the governing body for cricket in Ireland, awarded O'Brien a full-time "category A" contract in January 2010.
He was one of six players to be awarded such contracts with Cricket Ireland (four players received category B contracts and five category C), and came just a year after the first professional contracts were awarded to Ireland's cricketers.
Before that players were amateurs relying on income from other jobs and playing cricket in their spare time.
The contract allowed O'Brien and the others to focus on cricket, with the aim of improving ahead of the 2011 World Cup.


In Ireland's first match at the Sri Lanka Associates T20 Series against Afghanistan, O'Brien performed poorly overall.
With the bat he managed only 1 run from 2 balls before having to depart.
His bowling figures ended at 0–34, but Ireland managed to seal the win by 5 wickets.
In their second match against Canada, O'Brien finished with 0–38 in the Canadian innings, and 5 off 2 balls with the bat as Ireland narrowly lost by 4 runs.
In the third and final game (against Sri Lanka A), O'Brien ended the tournament wicketless after 0–15 off two overs.
He managed 11 off ten balls as Ireland put in a spirited performance but lost by 5 wickets.

In 2010, O'Brien was again nominated for the Associate and Affiliate Player of the Year Award, this time alongside two other Ireland players (there were 16 nominees in all); the award was given to Netherlands Ryan ten Doeschate.
O'Brien was selected in Ireland's 15-man squad for the 2011 World Cup hosted by Bangladesh, India, and Sri Lanka.
On 2 March O'Brien hit the fastest century in World Cup history, off just 50 balls against England helping his team to successfully chase down a target of 328 when at one stage they were struggling at 111/5.
In that World Cup match against England he along with Alex Cusack set the highest ever 6th wicket partnership in World Cup history (162).
Ireland won two of their matches, but failed to progress beyond the first round, finishing six out of seven in their group.
With 198 runs at an average of 39.60, O'Brien finished as Ireland's second highest run-scorer in the tournament.
On 23 May 2013, at Clontarf Cricket Club Ground, Dublin, he scored an unbeaten 84 in 47 balls against Pakistan which helped the Ireland to tie the match.
Ireland required 15 runs in the last over to win the match, O'Brien hit last ball of Saeed Ajmal to boundary to pull out a thrilling 'tie' for the Irish team.
Cricket Ireland, the governing body for cricket in Ireland, awarded O'Brien a full-time "category A" contract in January 2010. He was one of six players to be awarded such contracts with Cricket Ireland (four players received category B contracts and five category C), and came just a year after the first professional contracts were awarded to Ireland's cricketers. Before that players were amateurs relying on income from other jobs and playing cricket in their spare time. The contract allowed O'Brien and the others to focus on cricket, with the aim of improving ahead of the 2011 World Cup.

In Ireland's first match at the Sri Lanka Associates T20 Series against Afghanistan, O'Brien performed poorly overall. With the bat he managed only 1 run from 2 balls before having to depart. His bowling figures ended at 0–34, but Ireland managed to seal the win by 5 wickets. In their second match against Canada, O'Brien finished with 0–38 in the Canadian innings, and 5 off 2 balls with the bat as Ireland narrowly lost by 4 runs. In the third and final game (against Sri Lanka A), O'Brien ended the tournament wicketless after 0–15 off two overs. He managed 11 off ten balls as Ireland put in a spirited performance but lost by 5 wickets. 
In 2010, O'Brien was again nominated for the Associate and Affiliate Player of the Year Award, this time alongside two other Ireland players (there were 16 nominees in all); the award was given to Netherlands Ryan ten Doeschate. O'Brien was selected in Ireland's 15-man squad for the 2011 World Cup hosted by Bangladesh, India, and Sri Lanka. On 2 March O'Brien hit the fastest century in World Cup history, off just 50 balls against England helping his team to successfully chase down a target of 328 when at one stage they were struggling at 111/5. In that World Cup match against England he along with Alex Cusack set the highest ever 6th wicket partnership in World Cup history (162). Ireland won two of their matches, but failed to progress beyond the first round, finishing six out of seven in their group. With 198 runs at an average of 39.60, O'Brien finished as Ireland's second highest run-scorer in the tournament. On 23 May 2013, at Clontarf Cricket Club Ground, Dublin, he scored an unbeaten 84 in 47 balls against Pakistan which helped the Ireland to tie the match. Ireland required 15 runs in the last over to win the match, O'Brien hit last ball of Saeed Ajmal to boundary to pull out a thrilling 'tie' for the Irish team.
Kevin O'Brien (cricketer)