Eispiraten Crimmitschau (the Ice Pirates) announced the signings on its website today.
It says both players will receive 30-day contracts.
Simmonds and Stewart could debut at home against the Lausitzer Fuechse on Friday.
They are the first foreigners to sign for a German team during the lockout.
Buffalo Sabres defenceman Christian Ehrhoff signed with his hometown team, the Krefeld Penguins.