The 27-year old winger, who was named the All India Football Federation's Player of the Year last season, will jet out from Kolkata on Friday to link up with the Washington club.
Nabi will then return to Mumbai to club training with IMG-Reliance after his week-long stay with DC.
"I'm looking forward to this trip as the training there would help me immensely. I will get around a week to prove myself," he told the Times of India.
Nabi, who has appeared 61 times for India, played with Mohun Bagan last season but is yet to sign with a new I-League outfit despite coming to an agreement with IMG-R.