The move, following a three-way pitch, means that for the first time since comms director Mark Fox was appointed two years ago, one agency will handle both briefs.
Financial PR was previously handled by Hudson Sandler, which is understood to have pitched. City PR firm Smithfield is also believed to have been a contender.
It is understood that Fox had favoured the integration of both accounts.
He said: 'This marks another step up for the BVCA's corporate and public affairs work.'
He added that a key aspect of H&K's work was to gain better recognition among the financial community of the role its members play in the economy.
The H&K account team is led by director Simon Miller.