At the 2008 Summer Olympics in Beijing, he participated in the 4 × 100-metre freestyle relay, 4 × 200-metre freestyle, and 4 × 100-metre medley.
2009–2012
At the 2009 World Aquatics Championships in Rome, along with César Cielo, Guilherme Roth, and Fernando Silva, he finished 4th in the 4 × 100-metre freestyle relay; with Thiago Pereira, Rodrigo Castro, and Lucas Salatta, he got the 10th place in the 4 × 200-metre freestyle. He also competed in the 100-metre freestyle finals, placing 8th, and finished in 18th place in the 200-metre freestyle. He competed in the 2010 Pan Pacific Swimming Championships in Irvine, where he finished 5th in the 4 × 200-metre freestyle, 12th in the 100-metre freestyle, and 22nd in the 200-metre freestyle. At the 2010 FINA World Swimming Championships held in Dubai, the Brazilian national team, composed of César Cielo, Nicholas Santos, Marcelo Chierighini, and Nicolas Oliveira, won the bronze medal in the 4 × 100-metre freestyle, with a time of 3:05.74, with Brazil beating the American team. He also won the bronze medal in the 4 × 100-metre medley race, by participating at heats. Participating in the 2011 World Aquatics Championships held in Shanghai, Oliviera finished 13th in the 200-metre freestyle, 9th in the 4 × 100-metre freestyle, and 14th in the 4 × 200-metre freestyle. He was in 2011 Summer Universiade, where he won the silver medal in the 4 × 100-metre freestyle. At the 2011 Pan American Games in Guadalajara, Oliviera won the gold medal in the 4 × 100-metre freestyle relay and silver in the 4 × 200-metre freestyle. He also came in ninth place in the 200-metre freestyle.
At the 2012 Summer Olympics in London, Oliveira finished 9th in the 4 × 100-metre freestyle and 24th in the 100-metre freestyle.
2012–2016
Frustration with the result in England made the Brazilian withdraw from swimming for six months. Oliveira went through a difficult process to rebuild, but he returned to compete. At the 2013 World Aquatics Championships in Barcelona, he finished seventh in the 4 ×100-metre freestyle, along with Fernando Santos, Marcelo Chierighini, and Vinícius Waked. In the 200-metre freestyle, Oliveira classified to the semifinals with the best time of his life without super suits, 1:46.99. In the semifinals, he swam a half second above the qualification time, finishing 11th. He also finished 11th in the 4 × 200-metre freestyle, along with João de Lucca, Fernando Santos, and Vinícius Waked. At the 2014 Pan Pacific Swimming Championships in Gold Coast, Queensland, Australia, Oliveira won a bronze medal in the Brazilian 4 × 100-metre freestyle relay, along with João de Lucca, Marcelo Chierighini, and Bruno Fratus. He also finished 5th in the 100-metre freestyle, 6th in the 200-metre freestyle, and 17th in the 50-metre freestyle. At the 2015 Pan American Games in Toronto, Canada, Oliveira won a gold medal in the 4×200-metre freestyle relay, where he broke the Pan Am Games record with a time of 7:11.15, along with Luiz Altamir Melo, Thiago Pereira and João de Lucca, and finished 5th in the 200-metre freestyle. He also won a gold medal in the 4×100-metre freestyle relay, by participating at heats. At the 2015 World Aquatics Championships in Kazan, he finished 15th in the Men's 4 × 200 metre freestyle relay, along with João de Lucca, Thiago Pereira and Luiz Altamir Melo., and 22nd in the Men's 200 metre freestyle.
Oliveira competed for the last time at the 2016 Summer Olympics, where he went to the Men's 4 × 100 metre freestyle relay final, finishing in 5th place. He also competed in the Men's 4 × 200 metre freestyle relay, where the Brazilian relay finished in 15th place, and in the Men's 100 metre freestyle, finishing 28th. At 29 years old, he said goodbye to swimming after three Olympic Games, and six World Championships.
Records
Nicolas Oliveira is the current holder, or former holder, of the following records: Long course :
Former South American record holder of the 200-metre freestyle: 1:46.90, time obtained on May 6, 2009
South American record holder of the 4 × 100-metre freestyle: 3:10.80, time obtained on July 26, 2009, along with Guilherme Roth, Fernando Silva, and César Cielo
South American record holder of the 4 × 200-metre freestyle: 7:09.71, time obtained on July 31, 2009, along with Thiago Pereira, Rodrigo Castro, and Lucas Salatta
Former South American record holder of the 100-metre freestyle: 46.30, time obtained on November 14, 2009
Former South American record holder of the 200-metre freestyle: 1:42.01, time obtained on November 15, 2009
South American record holder of the 4 × 100-metre freestyle: 3:05.74, time obtained on December 15, 2010, along with Nicholas Santos, Marcelo Chierighini, and César Cielo
