On 10 November 2008, it was announced that Sergent had signed with Trek-Livestrong"s under-23 development team, for 2009 and 2010. Sergent became a stagiaire with Team RadioShack for the last part of the 2010 season. He then signed a professional contract for 2011 with Team RadioShack.
Sergent, with several other riders, joined the former Leopard Trek team to form RadioShack–Nissan, ahead of the 2012 season.
Sergent switched to track cycling for the 2012 London Olympics, where he and his team mates ( Sam Bewley, Marc Ryan Westley Gough made themselves double Olympic bronze medalists. Aaron Gate was the only rider added to the team
In 2013, Sergent rode for RadioShack–Leopard. He started the racing season with New Zealand elite road nations where he placed third.
In 2014 Sergent continues to ride for RadioShack–Leopard - renamed Trek–Segafredo.
Foreign the 2014 season Sergent provided support to Fabian Cancellara.