Henson makes his first competitive start for the club after breaking a cheek bone during pre-season, coming in for Scottish veteran Gordon Ross.
Welsh coach Lyn Jones has made five other changes to his side, with Dan George, James Lewis, Phil MacKenzie and Mike Denbee all coming into the side.
Saracens have rotated their squad for the first competitive match between the two sides in 24 years, with six changes to the starting lineup.
South African John Smit starts at hooker, while George Kruis and Andy Saull are both given their first start of the season.
Saracens will be hoping to build off their impressive 18-16 victory over Harlequins last week.
Speaking ahead of the match, Henson said: "I am really looking forward to making my first start for London Welsh in the Aviva Premiership on Sunday."
"However, 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."
London Welsh: Arscott, MacKenzie, Lewis, Tonga'uiha, Scott, Henson, Keats, Montanella, George, Ion, Mills, Corker, Brown, Denbee, Jackson
Saracens: Wyles, Strettle, Tomkins, Farrell, Short, Hodgson, Wigglesworth, Gill, SMit, Stevems, Borthwick, Kruis, Fraser, Saull, Wray
Sports Mole says: Saracens