Jenkins, a former merchant banker, is on secondment from UnLtd to the Big Lottery Fund and the National Endowment for Science, Technology and the Arts, working on projects related to the development of Big Society Capital, formerly known as the Big Society Bank.
He will take over at the Social Investment Business on 26 September and replaces Jonathan Lewis, who left in July to run Bromley Healthcare, an independent social enterprise spun out of the NHS.
In a statement, Jenkins said: "This is a really exciting time to be joining the Social Investment Business. There are lots of opportunities in the social investment market and the Social Investment Business is ideally placed to develop these."
The Social Investment Business manages several government funds, including the Social Enterprise Investment Fund, which helps health organisations to become social enterprises, and Communitybuilders, a permanent endowment that lends to community organisations. It also ran the Futurebuilders fund and is involved in setting up a number of third sector consortia.