Lehmus, who has been with the company since 1998, will replace Peter Vanacker who resigned as CEO in December and is due to step down by the end of April.
Under Vanacker's leadership, Neste has expanded its renewables business targeting to become the world's first renewable fuels maker with global capacity.
Lehmus takes over as the company accelerates its renewables push, with a final investment decision pending for building a biofuels refinery in the Dutch port of Rotterdam while its also developing a joint venture with Marathon to make renewable diesel in California.
Lehmus has held several leadership positions during his career with the company, in both its oil products business and renewables, the company said.
Neste conducted an international recruitment process to find suitable candidates for the position but eventually chose an internal successor, Neste's chairman of the board Matti Kahkonen said in a statement.
"The choice is supported by his long history at Neste and the experience of recent years in the Renewable Products business, around which Neste's growth strategy is built," Inderes analyst Petri Gostowski wrote in a note regarding Lehmus's appointment.
He saw the appointment of a company insider as positive, saying it enables a smooth transition.
Vanacker had led Neste since November 2018, and just days after his resignation from Neste in December, Dutch chemical company Lyondell Basell Industries appointed Vanacker as CEO on a base salary of $1.4 million.
At Lyondell, he will replace Bhavesh Patel, who in January joined private chemicals company W. R. Grace & Co as CEO.
Analysts saw Vanacker's resignation as "surprising", saying he had succeeded in the implementation of the company's strategy.
(Reporting by Boleslaw Lasocki in Gdansk and Anne Kauranen in Helsinki; editing by Sherry Jacob-Phillips and Jason Neely)
