The 20-year-old stepped up to take a penalty in the shoot-out against PSG on Wednesday, but side-footed his effort well wide.
Tottenham went on to lose the Super Cup 4-3 on penalties, despite going 2-0 up against the Champions League winners in the first half.
In the aftermath, the young forward was racially abused on social media, with his club coming out in support of Tel, and branding the perpetrators as ‘cowards.’
"Mathys showed bravery and courage to step forward and take a penalty, yet those who abuse him are nothing but cowards - hiding behind anonymous usernames and profiles to spout their abhorrent views," Tottenham said.
"We will work with the authorities and social media platforms to take the strongest possible action against any individual we are able to identify.
"We stand with you, Mathys."