Herbert, winner of three grands prix with Benetton and Stewart in the 1990s, was hired as sporting relations manager in 2005 to improve the team's public image in their final year as Jordan.
Midland were bought by Spyker this month, with the takeover approved by shareholders on Thursday.
Team boss Colin Kolles said Herbert's departure was a natural consequence of the takeover by Spyker, with the 42-year-old employed by Midland's parent company rather than the team itself.
"Of course, he was part of the team but it was a different arrangement," he said at the Chinese Grand Prix on Friday.
Michiel Mol, a Spyker shareholder and their new director of Formula One racing, said the Briton's future with the team remained open, however.
"I have spoken with Johnny and somewhere in the next week or two we'll sit down and have a chat to see if there is a future or not. At the moment I don't know yet," he said.
"His deal with Midland finished and now we have to see whether we can do something with him in the future."
