The outsourcing and energy services firm said the deal is expected to generate revenues of about £170mln per year.
Mitie has been delivering services to Lloyds since 2012 and new agreement extends the partnership though to the end of 2024.
The extended contract covers 30 service lines including engineering, security, cleaning and data centre management that will be provided the bank’s branches and offices across the UK.
The deal has already been factored into the group’s guidance for the 2020 financial year.
"I'm delighted that we have agreed to extend our contract with LBG, our largest client, until 2024 and that we have done so under a breakthrough 'payment by results' structure which will ensure that all LBG's branches and facilities are maintained to the very highest levels,” said Mitie chief executive Phil Bentley.