The companies stressed the proposed transfer will not affect Motorola's existing licensing arrangement with Symbian. However, Motorola said its primary software focus for the mass market is now centred on Java, which is also supported by Symbian.
The share transfers are still subject to approval by the German Federal Cartel Office, and to a preemption procedure among other Symbian shareholders, which include Sony Ericsson, Ericsson, Samsung and Panasonic. The companies said they expect to complete the deal within weeks.
Though exact figures were not revealed, the transaction implies a value for Symbian of US$420 million.
"The investment shows Nokia's continued support to Symbian as a strong independent software licensing company and to its stable development as smart phones move towards the volume market. Symbian has proven that it is fully able to meet the different needs of its licensees by providing the most optimized operating system for feature rich mobile devices," Pertti Korhonen, executive vice president, Nokia Mobile Software, said in a statement.
Scott Durchslag, corporate vice president of Motorola's Personal Communications Sector, added: "As a Symbian licensee, Motorola will continue to support the Symbian OS for specific customer and business needs such as in our 3G devices. However, our primary software focus for the mass market will stay centered on Java.
"We believe Java is what ultimately provides our customers worldwide with the most optimised and differentiated mobile experiences."