Thuram headed into the net in the 41st minute of the match to put his team 2-0 ahead, then dropped to one knee in a gesture reminiscent of that by former NFL quarterback Colin Kaepernick and his protests against racial injustice in the US.
The revival of the symbol by the 22-year-old Thuram comes as protests continue to rage across the US after the death of African American George Floyd at the hands of police in Minneapolis.
Thuram – who is the son of French World Cup winner and national footballing icon Lilian Thuram – struck again in the 59th minute of the game against Union at the Borussia-Park stadium, restoring a two-goal cushion after Sebastian Andersson had pulled a goal back for the visitors.
Alassane Plea then added a fourth late on as Moenchengladbach moved up to third in the table, keeping themselves firmly in the hunt for Champions League football.
On Saturday US international Weston McKennie, who plays for Bundesliga team Schalke 04, wore an armband with the message “Justice for George” written on it in his team’s match against Werder Bremen.