The advice giant has joined the trade body following "a change of pace and innovation" in the equity release sector, the Equity Release Council said.
It also reported a growing membership as the amount of individuals signed up rose 50% over the last two years to more than 1,500, while the number of firms signed up has passed the 600 mark.
Equity release market breaks Q1 record
"We have been providing equity release for over 15 years and, with the market developing at such a pace, we want to ensure we continue to maintain the high standards of advice required for clients to take out equity release plans," said SJP head of mortgages Paul Johnson.
"The Equity Release Council continues to lead the way in developing the highest standards of consumer-focused advice, so our partnership is a natural evolution of our work in this sector. We are looking forward to benefiting from the ongoing support the Council provides to the industry."
Equity Release Council CEO Jim Boyd said SJP's membership was a "vote of confidence" in modern equity release and its "rigorous standards".
He continued: "St James Place' has long recognised that equity release offers an important option for its clients. Its support underlines that today's products play a multi-functional role for a broad mix of customers, including those considered high net worth.
"Our growing membership is becoming increasingly diverse as wealth managers, pensions specialists and mortgage advisers find their clients weighing up a host of decisions in later life, from care planning to the transfer of wealth between generations."