Former France international Henry served as second assistant to manager Roberto Martinez during Belgium’s run to the semi-finals at the 2018 World Cup.
Henry, Arsenal’s all-time leading scorer, was then promoted to Martinez’s number two before he became the manager of Monaco in October of the same year.
The Belgium national team tweeted: “Unfinished business. We welcome back Thierry Henry in the staff for #EURO2020!”
Henry, 43, most recently served as the manager of MLS side Montreal Impact before quitting his post in February.
Henry, who also played for Barcelona and Monaco, is due to be part of the BBC’s punditry team for this summer’s tournament.
Belgium, who are considered among the favourites to win the tournament, have been paired with Russia, Finland and Denmark in Group B.
They open their campaign against Russia on June 12.
Additional reporting by PA.