Children aged eight and nine returning to the UK from abroad will be able to use e-gates at airports and other re-entry points from 8 July, the Home Office has announced.
They need to be at least 120cm (3ft 11in) tall so they can be seen by the biometric scanners and must be accompanied by an adult.
By lowering the minimum age from ten, the government believes up to 1.5 million additional children will be able to use e-gates.
More than 290 e-gates in the UK and at juxtaposed ports, where border checks take place on the continent, are involved.
Minister for Migration and Citizenship Mike Tapp said more families would "experience a swifter and smoother journey home... this summer holiday season".
E-gates are designed to speed up passenger border checks through a digital passport scan.
Those in the UK will be available to Britons as well as citizens of EU states, Australia, Canada, Iceland, Japan, Liechtenstein, New Zealand, Norway, Singapore, South Korea, Switzerland and the US, and members of the Registered Traveller Service.
Border Force Director General Phil Douglas said the new measure allowed "highly skilled officers to focus on intercepting those who pose a threat to the UK".
Karen Dee, Chief executive of AirportsUK, the trade body for UK airports, called it a "welcome development".
"It will give more families the ability to take advantage of this technology, speeding up the border process and reducing waiting times for many," she said.
"Airports work very hard with border authorities to ensure the UK's front door is both secure and welcoming, with those coming home and visiting enjoying a smooth experience."
The e-gates are installed across 13 airports in the UK: Birmingham, Bristol, Cardiff, East Midlands, Edinburgh, Gatwick, Glasgow, Heathrow, London City, Luton, Manchester, Newcastle and Stansted.
They are also available in juxtaposed ports in Brussels and Paris.
E-gates are part of the government's Electronic Travel Authorisation (ETA) scheme which rolled out in February, providing digital permission for people to arrive in the UK.
Under the new system, travellers from visa-free countries like Canada and Australia now require an ETA to arrive in Britain at a cost of £20.
Digital passport checks caused long disruptions at some airports in Europe, including Italy and Portugal, in recent months, leading to warnings that new passport scanning systems could cause major delays over the summer.
