In 1999, O'Driscoll was selected for the senior squad and was on the bench for a match against Italy, although he did not play.
He won his first Test cap at age 20 on 12 June 1999 in a 46–10 loss to Australia in Brisbane as part of the tour of Australia.
O'Driscoll played for Ireland before he played for the senior Leinster team.

In 2000, O'Driscoll scored a Hat-trick of tries in a Six Nations Championship victory against France in Paris, propelling Ireland to their first win in Paris since 1972.

O'Driscoll's popularity in Ireland was expressed by supporters wearing T-shirts bearing the motto "In BOD We Trust".
In 2002, O'Driscoll was handed the captaincy for the first time in Ireland's 18–9 win over Australia, the first Irish victory over the Wallabies since 1979.
In 2003, following the international retirement of long-time Ireland captain Keith Wood, O'Driscoll was awarded the captaincy on a permanent basis.
In that year, O'Driscoll led Ireland to second place in the Six Nations Championship.
This was followed by Triple Crowns in 2004 (Ireland's first crown since 1985), 2006 and 2007.
In 2004, O'Driscoll captained Ireland to a 17–12 victory over South Africa, the first Irish win over the Springboks since 1965.

In 2009, O'Driscoll was again selected as captain, leading Ireland to win the Triple Crown, Six Nations Championship and their first Grand Slam in 61 years.
He scored a try in every match except one, culminating in a 17–15 victory in Cardiff in which O'Driscoll again scored a try and was the RBS man of the match.
On 27 March 2009, he was named as player of the 2009 Six Nations Championship, winning the fans' online poll.
In May 2009, he was named the Bord Gáis Energy IRUPA Players' Player of the Year for the past season.

On 15 November 2009, in a 20–20 draw against Australia at Croke Park, O'Driscoll scored a last minute try.
The next day, he was named as one of the seven nominations for the 2009 International Rugby Board player of the year, but controversially missed out to Richie McCaw for this title by a solitary point.

O'Driscoll started for and captained Ireland for every match during the 2010 Six Nations Championship.
He picked up his 100th test cap for Ireland against Wales.
He scored his 40th test try against New Zealand on 12 June 2010.
He started every match for Ireland in the 2010 Autumn Tests.
He played for Ireland in the last four World Cups (17 caps, 7 tries).
He became Ireland's most capped player on 26 June 2010 against Australia, winning his 103rd cap.

In the 2011 Six Nations Championship, O'Driscoll's 47th minute try against England, took him past Ian Smith's 78-year-old record of 24 tries to become the leading Championship try scorer of all time with 25 Tries.
The same day, O'Driscoll tied John Smit's International Captaincy caps record of 75.

O'Driscoll was ruled out of the entire 2012 Six Nations after undergoing shoulder surgery.
In his absence, Keith Earls was chosen to partner inside centre Gordon D'Arcy, starting four of the five championship games in the position usually occupied by O'Driscoll.

He returned as captain for the tour of New Zealand in 2012 and he also equalled John Smit's record as captaining an international side (83 times) but All Black Captain Richie McCaw tied the O'Driscoll/Smit record during the 2013 Rugby Championship against South Africa and McCaw overtook the record when playing in Japan on 2 November 2013.
O'Driscoll was fit to play in the 2013 tournament, but before the tournament it was announced that O'Driscoll, who had missed the Autumn internationals earlier that season through injury, would not be reinstated as captain.
Declan Kidney named O'Driscoll's Leinster teammate Jamie Heaslip as captain, in his place.
O'Driscoll still started each game of the game of the 2013 Championship for Ireland.

On 8 March 2014, in his last home international for Ireland, O'Driscoll led the team out against Italy in the 2014 Six Nations Championship and contributed to three tries in the game as Ireland won 46–7, for which he was awarded Man of the Match.
At this point O'Driscoll
In 1999, O'Driscoll was selected for the senior squad and was on the bench for a match against Italy, although he did not play. He won his first Test cap at age 20 on 12 June 1999 in a 46–10 loss to Australia in Brisbane as part of the tour of Australia. O'Driscoll played for Ireland before he played for the senior Leinster team.
In 2000, O'Driscoll scored a Hat-trick of tries in a Six Nations Championship victory against France in Paris, propelling Ireland to their first win in Paris since 1972.
O'Driscoll's popularity in Ireland was expressed by supporters wearing T-shirts bearing the motto "In BOD We Trust". In 2002, O'Driscoll was handed the captaincy for the first time in Ireland's 18–9 win over Australia, the first Irish victory over the Wallabies since 1979. In 2003, following the international retirement of long-time Ireland captain Keith Wood, O'Driscoll was awarded the captaincy on a permanent basis. In that year, O'Driscoll led Ireland to second place in the Six Nations Championship. This was followed by Triple Crowns in 2004 (Ireland's first crown since 1985), 2006 and 2007. In 2004, O'Driscoll captained Ireland to a 17–12 victory over South Africa, the first Irish win over the Springboks since 1965.
In 2009, O'Driscoll was again selected as captain, leading Ireland to win the Triple Crown, Six Nations Championship and their first Grand Slam in 61 years. He scored a try in every match except one, culminating in a 17–15 victory in Cardiff in which O'Driscoll again scored a try and was the RBS man of the match. On 27 March 2009, he was named as player of the 2009 Six Nations Championship, winning the fans' online poll. In May 2009, he was named the Bord Gáis Energy IRUPA Players' Player of the Year for the past season.
On 15 November 2009, in a 20–20 draw against Australia at Croke Park, O'Driscoll scored a last minute try. The next day, he was named as one of the seven nominations for the 2009 International Rugby Board player of the year, but controversially missed out to Richie McCaw for this title by a solitary point.
O'Driscoll started for and captained Ireland for every match during the 2010 Six Nations Championship. He picked up his 100th test cap for Ireland against Wales. He scored his 40th test try against New Zealand on 12 June 2010. He started every match for Ireland in the 2010 Autumn Tests. He played for Ireland in the last four World Cups (17 caps, 7 tries). He became Ireland's most capped player on 26 June 2010 against Australia, winning his 103rd cap.
In the 2011 Six Nations Championship, O'Driscoll's 47th minute try against England, took him past Ian Smith's 78-year-old record of 24 tries to become the leading Championship try scorer of all time with 25 Tries. The same day, O'Driscoll tied John Smit's International Captaincy caps record of 75.
O'Driscoll was ruled out of the entire 2012 Six Nations after undergoing shoulder surgery. In his absence, Keith Earls was chosen to partner inside centre Gordon D'Arcy, starting four of the five championship games in the position usually occupied by O'Driscoll.
He returned as captain for the tour of New Zealand in 2012 and he also equalled John Smit's record as captaining an international side (83 times) but All Black Captain Richie McCaw tied the O'Driscoll/Smit record during the 2013 Rugby Championship against South Africa and McCaw overtook the record when playing in Japan on 2 November 2013. O'Driscoll was fit to play in the 2013 tournament, but before the tournament it was announced that O'Driscoll, who had missed the Autumn internationals earlier that season through injury, would not be reinstated as captain. Declan Kidney named O'Driscoll's Leinster teammate Jamie Heaslip as captain, in his place. O'Driscoll still started each game of the game of the 2013 Championship for Ireland.
On 8 March 2014, in his last home international for Ireland, O'Driscoll led the team out against Italy in the 2014 Six Nations Championship and contributed to three tries in the game as Ireland won 46–7, for which he was awarded Man of the Match. At this point O'Driscoll
Brian O'Driscoll