The three-member court sentenced him over a high treason charge that has been pending against him since 2013.
Gen Musharraf seized power in a military coup in 1999 and served as the country's president from 2001 to 2008.
He is currently in Dubai after being allowed to leave the country for medical treatment in 2016.
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The charge relates to Gen Musharraf's suspension of the constitution in 2007, when he imposed emergency rule in a move intended to extend his tenure.
He is the first military ruler to ever stand trial in Pakistan for overruling the constitution.
The verdict was announced Tuesday with a 2-1 majority.