Leonardo MW is the UK wing of Italian defence giant Leonardo-Finmeccanica, though the firm has a burgeoning division that advises customers on the risks of cyber breaches.
Through the agreement, Leonardo will use Crossword's Rizikon cybersecurity product to help customers assess the security risks in dealing with suppliers across the world.
Leonardo's client list includes governments, defence and infrastructure companies both in the UK and internationally.
The companies also intend to collaborate on bids for “significant contracts across multiple industries” throughout 2020, using Crossword’s Rizikon Assurance and Leonardo's market expertise in integration, cyber and third-party assurance.
Jake Holloway, Crossword's director of business development called it a “big step in our development as a business”.
"Having Leonardo as a partner will allow us to respond to much larger opportunities for our products like Rizikon Assurance.”
In October, Crossword also inked a two-year contract with a FTSE250 chemicals company for Rizikon.
shares rose 10% to 458p in Tuesday morning trading.