Gower, 34, joined the club ahead of last season and has since signed a contract extension until the end of 2014.
Coach Tony Rea said: “At the conclusion of the pre-season camp in France I sat down with Craig at the airport in Toulouse and formally offered him the captaincy for the 2013.
“Craig’s actions and connection with the players around the club environment convinced me that he is their leader.
“We felt out of respect to the position and Craig, it was important to be clear that the leadership is not an entitlement but rather is something that is earned. Craig’s deeds earned him this honour.
“Craig looks forward to working with everyone involved with the club to ensure we are all achieving our best and are operating in a challenging and inspiring environment.”
London’s first game of the new season is against Widnes on Sunday.