McDermott Will & Emery is taking a partner from Nabarro Nathanson to set up what is thought to be the first pensions practice at a US firm in London.
Steven Hull will join to build a new practice which will fit in with the firm's existing international employment practice and top US-based pensions practice.
Last year the firm was the first US practice to set up an employment department when it poached Fraser Younson from Baker & McKenzie and David Dalgarno from Warner Cranston.
The firm is unusual as a US practice because it is building a full service firm in London.
Hull has been a partner in Nabarros' highly-rated pensions practice since 1997, and was seconded to Weil Gotshal & Manges in New York for two years. While there he acted for clients including General Electric Capital Corporation and General Motors.
Fraser Younson, head of employment at McDermotts, says: "McDermott Will & Emery is a long way along its road to being a full service corporate law firm.
"Right from the start we wanted to have strong departments across the board and we decided we would wait for the right people to become available.
"We always wanted a pensions practice and we started working towards this in the last quarter of last year. We wanted someone who is entrepreneurial and has the drive to establish and grow a top rate pensions practice."
Hull says that he was not looking for a move, but when he was approached by McDermotts he realised it was a rare opportunity to start something from scratch.
He says: "I believe it's the first US firm in London to do pensions. Most of the American practices focus on the finance side and banking work. But employment and pensions is the formula that has worked for McDermotts in the US."
He says he will be recruiting assistants to the practice as soon as he arrives, and may take on another partner in the future.