Green replaces Lord Roger Freeman who has asked to retire from the board, upon publication of the 2019 results.
Additionally, the company told investors it has also appointed Nicola Ham Edmonds, currently head of legal, as company secretary.
"On behalf of my fellow directors, I welcome Martin to the board as a non-executive director whose strategic and technical experience will add significant value to our discussions,” said chairman Roger Putnam.
“I thank Lord Freeman for his contribution to the direction of ITM Power over the past nine years and wish him well for the future. Finally, congratulations from all of us to Nicola on her appointment as company secretary."