Between December 15 and January 13, the airline will operate four flights a day to the Gulf capital, connecting to its global network.
Flights will be operated by a two-class Boeing 787-9 with 28 business and 271 economy seats.
The additional flight will depart Heathrow at 12.50pm arriving Abu Dhabi 11.45pm, with the return flight departing Abu Dhabi at 7.05am arriving Heathrow 11.00am.
James Harrison, Etihad general manager UK and Ireland, said: “This is a busy time for local guests travelling between both capitals and the extra service will allow more choice and flexibility in their travel.”
Etihad’s additional flight will operate alongside its three daily London-Abu Dhabi services using its three-class Airbus A380 aircraft.
The airline has also added additional peak season capacity for onward connections from Abu Dhabi to Bahrain, Belgrade, Cairo, Istanbul, Medina and Kuwait.