BBA president Mohit Kamboj along with some others joined BJP in the presence of senior party leader Gopinath Munde here yesterday.
BBA had extended its support to Modi as the UPA government had brought about a "policy paralysis" in the economy, Kamboj said.
"There are over 50 lakh workers associated with the bullion and gold industry, which has been facing the brunt of the current policies of the UPA government.
Members of Bharat Diamond Bourse have said they will host Modi at a function at Bandra-Kurla Complex here on Sept. 30.
BJP president Rajnath Singh had last week inaugurated the BBA corporate office at Zaveri Bazaar here.