In 2004, at the age of just 20, he captained the New Zealand sevens team to its fifth IRB Sevens World Series title and in 2005 led the team to the final. Messam also played in the New Zealand sevens teams that won gold at the 2006 Commonwealth Games and 2010 Commonwealth Games. In 2004 he was also named New Zealand Sevens Player of the Year.

In October 2008, Messam was selected in New Zealand’s end of year tour squad to tour Hong Kong and Europe. He played one test against Scotland and one match against Munster. He subsequently appeared several more times for New Zealand but was dropped a month out of the 2011 Rugby World Cup in favour of Victor Vito. Since his debut in 2008 he won 40 test caps for the All Blacks.

Of Māori descent, Messam affiliates to the Ngāi Tūhoe iwi. Messam has stated that he also has Samoan and Scottish heritage. He has played for the New Zealand Maori, including during the 2006 Churchill Cup and the 2010 centenary series, where he captained the side. In 2012 and 2013 Messam was awarded the Tom French Cup as Māori Player of the Year.

Liam Mesam’s brother played in the 2012 All Whites side at the 2012 London Olympics.

On 31 January 2015, Messam fought on the undercard of close friend Sonny Bill Williams’ boxing bout.

Messam was selected for the 2015 Rugby World Cup as part of the All Blacks’ 31-man squad. After the tournament was finished, Messam announced his intention to compete in rugby sevens for the 2016 Summer Olympics. Messam was later named in the All Black Sevens’ squad for the Wellington Sevens alongside All Blacks teammate Sonny Bill Williams. After the Rio 2016 Summer Olympics, Liam Messam did play for the Chiefs in 2016 Super Rugby competition, when injuries greatly affected the loose forwards positions .

Throughout his professional athlete career Liam developed a preference for natural alternative health options to relieve both physical pain and mental challenges high-profile athletes experience. After witnessing the detrimental effect conventional pain relief and mental health medication has on close friends and family, Liam founded Ora CBD alongside Teddy Stanaway in 2020.