Catlin has agreed to occupy an additional 10,000 square feet of office space on the seventh floor of the London Underwriting Centre (LUC).
Catlin already occupies 22,000 square feet of the building the entire sixth floor.
The Lloyd's insurer has also extended its lease with the LUC from 2006 to 2016.
Catlin chairman Stephen Catlin said: "The LUC is now widely regarded as a centre of excellence in the insurance market. Its proximity to Lloyd¹s is ideal and it offers first-class services and facilities."
