The increased shareholding gives the company full control of the project's funding and execution, while the holder of the remaining interest, BMR Group, will keep a maximum 12.5% of generated earnings.
BMR agreed to up Jubilee's fully paid-up shareholding in the project when the shareholders' and operating agreements were updated to "better align with Jubilee's role to deliver a successful project".
Jubilee owns a 29.01% shareholding in BMR, in essence giving it a 91.5% holding in Kabwe.
The market was in favour of the move, with Jubilee's shares rising 11.67% Monday to 2.79p (US3.61c).
Under the agreement, if Jubilee invests more than US$15 million in the project, BMR's shareholding will dilute to 11%.
The company will also retain the right to increase its ownership to 100% within a two-year period, although will first have to receive all regulatory consent and pay all relevant taxes.
If the option is exercised, BMR will be granted royalty interest of either 11% or 12.5%, depending on Jubilee's capital investment, in Kabwe's distributable earnings, after costs, taxes, liabilities and depreciation have been factored in and Jubilee has secured a minimum 20% return on its investment.
Jubilee said, besides an initial 5% royalty, BMR's payments would only take place once Kabwe was fully operational and Jubilee had repaid all of its capital investment and the agreed capital rate of return of 30% on the first £2.3 million invested and 20% on any further capital invested.
Jubilee CEO Leon Coetzer said the agreement would "ensure that the success of the Kabwe project remains independent of the financial position of BMR with the option to acquire 100%".
Zambia's minister of mines and mineral development reinstated Kabwe's mining licence in April on the condition that plant construction start within three months, commissioning be done by September 30 and first production by December 30.