The Delhi-based franchise roped in Ashwin after a successful trade with KXIP ahead of the annual player action in December last year.
Ashwin has played 139 IPL matches so far and the off-spinner has picked up 125 wickets at an average of 26.43 and economy rate of 6.79.
Delhi Capitals have included the likes of Ajinkya Rahane, Ashwin and Marcus Stoinis as they look to win their maiden IPL title this year.
Delhi will face Kings XI Punjab in Dubai on September 20 to start their IPL 2020 campaign.
In their last group stage match, Delhi Capitals will take on Royal Challengers Bangalore in Abu Dhabi on November 2.
The 13th edition of the cash-rich league is set to begin on Saturday with the defending champions Mumbai Indians taking on Chennai Super Kings in Abu Dhabi.
The 53-day long tournament will be played across three venues -- Sharjah, Dubai and Abu Dhabi.