The 22-year-old joins the 18th placed side from Serbian Super Liga club FK Vojvodina on a three-and-a-half-year contract, for an undisclosed fee.
Sichenje has previously turned out for Kenyan side AFC Leopards, Swedish team AIK.
Addicks managing director James Rodwell told BBC Sport: "He's a player we've been tracking for a long time and was originally budgeted to join us this summer as part of our multi-window strategy to move the club forward.
"We're pleased that the opportunity arose for him to join us earlier than we expected and are grateful to the ownership for their support in enabling us to bring him to the football club at this stage."
Sichenje expressed his delight at the move, adding: "It's a big step for my career. It's a good opportunity to keep working, developing and help the team, so I just need to be humble and keep working - that's the goal."
Sichenje joins fellow new signings Harry Clarke, Lyndon Dykes, Luke Chambers, Tiernan Brooks, Jayden Fevrier and Conor Coady to the Championship side.
Kenya's two most celebrated football clubs, Gor Mahia and AFC Leopards, are facing a home-ground crisis as the government prepares to close Nyayo and Kasarani Stadium for renovations ahead of the 2027 AFCON.
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