The Brighton Pavilion MP and the co-accused were also cleared of committing a public order offence by Brighton Magistrates Court.
Lucas was arrested by police during an anti-fracking protest outside of Cuadrilla’s exploratory shale oil test drilling site in Balcombe, West Susses, on 19 August last year.
Following her acquittal, Lucas said: “This judgement is right but it is not a victory or a cause for celebration.
“We will continue to campaign fracking and will only celebrate when our world is a path to a clean energy future.”
She added: “The only place and responsible thing to do with shale gas is to leave it in the ground.
“Fracking will not lower our fuel bills, it will not give us energy security, and it will not create significant number of jobs.
“Fracking will accelerate climate change, pollute our environment, and lock us into yet more dependence on fossil fuels precisely when the overwhelming scientific and political consensus confirms that we need to move urgently in the opposite direction.”
The other protesters who were also cleared were: Josef Dobraszczyk, 22, from Bristol; Ruth Jarman, 50, from Hampshire; Sheila Menon, 42, from London; and Ruth Potts, 39, from Devon.