The Wales centre has been sidelined since suffering a fractured cheekbone during the Exiles pre-season defeat to the Scarlets.
But the double Grand Slammer has replaced Gordon to pull on the number 10 jersey in his first Premiership appearance, against Saracens.
“I am really looking forward to making my first start for London Welsh in the Aviva Premiership on Sunday,” said the 30-year-old.
“Having been given the opportunity by Lyn Jones and the club to play in the Premiership, it was both disappointing and frustrating to pick up an injury against Scarlets in pre-season.”
The London club have silenced some of their doubters after winning two of their opening five fixtures in the Premiership and they sit ninth in the league table.
Henson has been impressed by the progress of his side and hopes to hit the ground running against his former club.
“The boys have done really well in the first five games and now I just cannot wait to start playing my part with the rest of the team,”
“I am also very excited about playing at the Kassam in front of the London Welsh supporters for the first time.
“Saracens are an extremely good side, we know that, but this is a great opportunity both for me and for London Welsh to test ourselves against one of the best teams in the Aviva Premiership.”
