The Renault-powered STR10 will break cover at 1700 local time (1600 GMT), with drivers Max Verstappen and Carlos Sainz Junior both in attendance.
The duo - who form an all-new rookie line-up for Toro Rosso this year - will split driving duties over the four days in Spain. Sainz Jr will be at the wheel on days one and three, with Verstappen taking over on the second and fourth days.
As it stands, Toro Rosso will be the third team to unveil their new car. McLaren are set to open proceedings, launching on January 29, with Ferrari following suit one day later. Mercedes, meanwhile, are braced to reveal their car on February 1, just before track action commences.