The authority will require firms seeking work worth more than £5m per year to publish a carbon reduction plan.
The move mirrors a policy introduced by the government last month, which related to contracts entered into by Whitehall departments and their external agencies - but did not include local authorities.
The suggestion for County Hall to adopt the same requirement was made by Green Party county councillor Gina Dowding at a meeting of the full council in July, when the authority pledged to investigate the possibility.
A cabinet meeting where the plan was approved heard that only five procurement exercises undertaken by the authority have exceeded £5m over the past two years.
However, members were told it was likely that the government would reduce that threshold in future and deputy council leader Alan Vincent said that training would be given to companies likely to fall within its scope at a later date.
He added: “Obviously, the smaller the company, the more difficult it is [to fulfil the requirement].
“The last thing we need to do is have Lancashire firms [unable to] actually bid for a contract because they don’t have a carbon reduction plan in place.”
Cabinet member for environment and climate change Shaun Turner said that some of the larger potential suppliers were already “actively pursuing their own decarbonisation strategy”.
Under the policy, which will come into force in January 2022, bidders will be obliged to provide detailed information about their current emissions and how they are reported, as well as the environmental management measures they have in place, including specific carbon reduction initiatives that will be applied when fulfilling the contract.
However, the very presence of a carbon-cutting plan will be sufficient for a firm to make a contract bid - its contents will not itself be fully evaluated as part of the tender exercise.
Speaking after the meeting, County Cllr Dowding welcomed the adoption of the policy, but claimed that it was at odds with a decision taken elsewhere on the same cabinet agenda in relation to the proposed route of a spine road to serve the Bailrigg Garden Village development.
“Cabinet agreed to the principle of the compulsory purchase of land necessary for building a new road link to the M6 in South Lancaster. This is supposedly to enable the development of around 9,000 houses.
“It's very disappointing that the county cabinet is not joining up what is said and what is done on reducing carbon emissions. The new development is designed around easy access to the motorway and therefore will create more car journeys, more pollution and more carbon - it's a very disappointing way forward,” County Cllr Dowding added.