Edgar Alain Mebe Ngo'o was found guilty on Wednesday of misappropriating 23 billion CFA francs (about 35 million euros) by over-billing, Pauline Amougou Koe said.
The 66-year-old plans to appeal, the lawyer added.
His wife was also sentenced to 10 years for complicity in the embezzlement of public funds, and several properties belonging to the couple were seized, Amougou Koe said.
Formerly a leading member of Cameroon's government for more than a decade, Mebe Ngo'o was once tipped to succeed President Paul Biya.
He was sacked from the government in 2018 where he had served from 2015 as transport minister after spending the six previous years at defense.
Before that, Mebe Ngo'o led the police force and ran the presidency's civil office.
In 2010, Cameroonian journalist Jules Koum Koum, who died in a road accident, had investigated an alleged over-billing scandal for military uniforms at the defense ministry when Mebe Ngo'o was minister.
For four years, he has been in provisional detention after being charged with diverting public funds and corruption.
In 2006, Cameroonian authorities launched a national operation to clamp down on corruption which led to the sentencing of several ex-ministers and company bosses.
Cameroon was ranked 142 out of 180 on Transparency International's corruption perceptions index in 2022.