After dropping a set for the first time this week, he recovered and won the second to even the match and then the third and rubber set after his Swedish opponent committed a key double-fault.
"I came here this week and saw the draw and knew it would be difficult and so it is unbelievable I'm standing here with the trophy," a shocked Llodra told London's BBC Sports.
His 2008 match record rose to 14-3, giving him more victories than all of 2007, when he went just 13-18.
The title was worth $250,000.
Soderling fell to 2-4 in six career singles finals.