It is a new role for the organisation and she will join the firm in January next year.
She was most recently national key account manager at Santander and has looked after key networks and distribution and helped build strategic relationships.
She has also worked as acting relationship manager at Mortgage Engine for around a year, and before that she worked at Morgan Stanley as head of packaged sales for the south for around two years.
Prior to that she worked as a key account manager at Platform for around seven years.
Shawbrook Bank purchased The Mortgage Lender earlier this year, having taken a minority share in the business in 2018.
Shawbrook said at the time that the main driver for the purchase was to strengthen its position and distribution in the residential and buy-to-let markets.
The Mortgage Lender has been growing its team, hiring Rachel Glue as a regional underwriter and Alice Baggott as a key account support manager.
Palmer said: “Joining TML at this stage of its growth journey, and at such an important time for specialist lending, is an opportunity I simply could not turn down. The brand’s culture, people and leadership are also huge draws.
“Real life lending is such an exciting mission and I look forward to playing a role in the next stage of TML’s growth, adding value to brokers and advisers.
“I’ve thoroughly enjoyed my time at Santander for Intermediaries and wish the team well for the future.”
Steve Griffiths, sales director at The Mortgage Lender, said: “Being able to attract talent of Sara’s calibre to our senior management team is testament to what The Mortgage Lender has achieved over the past year. Her wealth of expertise and experience will help drive the team onto the next level as we embark on ambitious plans for 2022.”