Among residential lenders, JPM’s mortgage division, Chase, ranks second nationwide.
Chief executive Jamie Dimon had appeared to demote Braunstein in July, during an executive reshuffle meant to help JPMorgan move on from a $6 billion trading loss. Braunstein, who became CFO in 2010, kept his title but started reporting to co-chief operating officer Matt Zames instead of directly to Dimon.
In October, reports surfaced that Braunstein would step down by the end of the year. The bank said that he would become a vice chairman after Lake replaces him "early next year."
Lake, 43, will also join the bank's operating committee and will report directly to Dimon, a spokesman said.
Lake has held multiple roles at JPMorgan, including her current position as CFO of JPMorgan's large consumer and community bank.