The agreement offers BHP the option to take a stake in three exploration areas that Mundoro holds in Serbia's Timok mining region, to the country's east.
Mundoro is a Canadian listed mining investment company that focuses on generating revenue from royalties.
The agreement comes as copper miners extend their hunt for the conductive metal used in power generation and after BHP signed a deal to acquire Australian copper miner OZ Minerals Ltd last year.
Miner Rio Tinto Ltd said in December it had not given up on its plans to develop a $2.4 billion lithium mine in the country after its licenses were revoked following protests sparked by environmental concerns about the planned mine.
(Reporting by Melanie Burton; Editing by David Gregorio)