Lewis only joined the club earlier in the season after leaving his role at Sheffield United shortly before the appointment of Steve Coakley, who left the Millers to take up the same role at Bramall Lane.
A club statement read: Rotherham United can confirm that Head of Commercial Steve Lewis has left the club by mutual consent.
The club would like to place on record our thanks to Steve for his hard work and commitment whilst with the club, where over the last several months he has played a key role in the development of our new stadium.
Rotherham United would like to wish Steve well for the future.