Staff will walk out over 4-6 May, 9-10 May and 25-27 May as part of the action, which the union said would cause "inevitable disruption and delays". It follows 10 days of strikes over Easter, which involved 1,400 security workers.
Announcing the latest action, Unite general secretary Sharon Graham said: “Yet again, we have a chief executive in John Holland-Kaye who thinks it is acceptable to boost his earnings by an eye watering 88%, from £800,000 to a staggering £1.5 million, while he denies his own workers a decent pay rise.
“This dispute is bound to escalate with more workers being balloted and disruption set to continue throughout the summer.”
A Heathrow spokesperson said: "We kept Heathrow running smoothly during the first 10 days of Unite’s failed industrial action, and passengers can have confidence that we will do so again this time.
“We will not let Unite disrupt the flow of visitors to the UK during such an important period for the country."
A total of 5,148 flights are scheduled to depart Heathrow over the eight days of strike action, according to aviation analytics firm Cirium, with just over half (2,621) operated by British Airways.
