The partnership will see SulAmérica health insurance unit Brasilsaúde sell its products at BB's branches for three years, with the possibility of an extension for another three years.
In a research note, Barclays Capital said the new partnership came as a positive surprise since SulAmérica bought out BB from Brasilsaúde last year.
The investment bank noted that access to BB's large branch network will boost SulAmérica's strategic position in the health insurance segment, and could help the insurer to grow faster than the market in the midterm.
Barclays Capital reiterated its overweight rating on SulAmérica as it sees upside potential for the stock, and "good momentum for outperformance in the short run."
SulAmérica is the largest insurance group in Brazil that is not controlled by a bank. BB is in the process of forming one of the country's biggest insurance groups through an alliance with Spain's Mapfre.