A London jury on Friday acquitted 23-year-old Salma Kabal of failing to disclose information to police.
Her husband, Ashik Ali, is one of three men convicted in February over an al-Qaida-inspired plot to explode knapsack bombs in Britain.
Eleven men have been convicted over the plot, which one conspirator was recorded saying would be "another 9/11."
Kabal was charged after police recorded her talking with her husband shortly before his arrest in 2011.
She insisted she had never believed he was a terrorist, and thought his talk of jihad was an attempt to leave their marriage.
Assistant Chief Constable Marcus Beal of West Midlands Police said the force respected the jury's decision.