Monaco's Falcao is suspected of failing to correctly declare 5.6 million euros ($6.1 million) of income earned from image rights between 2012 and 2013 while he was at Atletico Madrid.
He is suspected of using a web of shell companies in the British Virgin Islands, Ireland, Colombia and Panama to avoid taxes on the image rights income.
Mendes was summoned to appear before the court of instruction at Pozuelo de Alarcon, close to Madrid, on June 27.
The summons comes a day after Ronaldo was accused by Spanish prosecutors of evading 14.7 million euros in tax through offshore companies.
Mendes other clients include Manchester United goalkeeper David de Gea, United manager Jose Mourinho, Real Madrid attacker James Rodriguez and Chelsea striker Diego Costa.