Around 1,400 security officers at Heathrow Airport will strike for eight days next month.
Unite said the staff will walk out from 4-6 May, 9-10 May and 25-27 May in a dispute over pay.
It comes as Passport Office staff will strike for four days at the start of next month.
Public and Commercial Services (PCS) union members in all passport offices across the UK will walk out from 2-6 May.
Action so far has been limited to some staff in some offices, but the union announced an escalation on Wednesday to include all members in all offices.
Nearly 2,000 passport examiners are already taking part in a rolling strike but the new announcement means a further 1,000 staff – including interview officers, and those in administrative and anti-fraud roles – will also take part on four days in May.
Meanwhile, senior civil servants will vote on industrial action over pay for the first time in more than four decades.
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The FDA union, which represents senior civil servants, said its executive committee has voted to launch a ballot in response to the government’s decision last week to give civil servants a pay rise of between 4.5% and 5%.
It is the first time the union has approved a vote on national strikes over pay in more than 40 years.
The union said the government had left it with no choice after the way civil servants had been treated.
FDA general secretary Dave Penman said: “In my 23 years at the FDA and 10 years as general secretary, I have never found myself so utterly at a loss as to why the government would want to treat our members and the rest of the civil service in this way.
“If this is, as I suspect, a tactical decision to use the civil service to send a message elsewhere then not only is it a flawed one, but once again demonstrates that there are those in government who simply do not value the civil service in the way they do the rest of the public sector.”
