On 31 January 2007, he scored his maiden ODI century with an unbeaten 112 to guide his side to victory over Bermuda. He followed it up in his next game with 104 not out against Kenya. In the 2007 World Cup he was man of the match with 85 against Bangladesh during a Super Eight game, which Ireland won.

Porterfield scored his maiden first-class century in late August 2007. In a match against Bermuda as part of the 2007–08 ICC Intercontinental Cup, Porterfield scored 166 runs from 326 balls.

In the 2011 Cricket World Cup, Porterfield reached a fifty against the Netherlands. He hit 68 off 98 balls and helped his team to victory over the Netherlands.

Captaincy

Porterfield was appointed Ireland captain at the start of the 2008 season, succeeding Trent Johnston. Porterfield said "I've learnt a lot from Trent – he brought young players through, looked after them and he set an example by how he went about his game and how he prepared on and off the field. I may be young but I've plenty of experience of captaincy and I love it, being out there right in the mixer. I was vice-captain under Trent and I filled in when he was off the field so I've had a taste of it".

Despite being Ireland's official captain, Porterfield chose to represent his county (Gloucestershire) instead of leading Ireland in their ODIs against Scotland and New Zealand in July 2008 in an attempt to secure a permanent position at Gloucestershire. He said "It's definitely the hardest decision I've ever had to make ... I feel it's the right decision for me at this stage in my career".

Porterfield was one of seven Ireland players to be nominated for the 2009 Associate and Affiliate Player of the Year (there were fourteen nominees in all);