Musharraf was sentenced to death in absentia by a special court in December last year on treason charges stemming from his imposition of a state of emergency in 2007.
Musharraf had challenged the formation of a special court for the sole purpose of trying him for treason.
It was not immediately clear if the ruling by the High Court in Lahore would automatically nullify the death sentence, but Musharraf's side was confident.
"The Lahore High Court has nullified the decision about Pervez Musharraf," Azhar Siddique, Musharraf's lawyer, told Reuters.
Musharraf, who seized power in a 1999 coup and later ruled as president until 2008, remains out of the country on medical grounds.