Max Clifford, 71, whose celebrity clients have included TV music mogul Simon Cowell and US boxer Muhammad Ali, was charged with 11 counts of sexually assaulting seven girls aged 14 to 19 between 1966 and 1984.
A jury cleared him on two of these charges and was unable to reach a verdict on the final charge, a spokeswoman for the Crown Prosecution Service said. Sentencing will take place on Friday.
Clifford was arrested in December 2012 as part of an investigation into historic sexual assault cases, code-named Operation Yewtree, triggered by revelations that the late BBC TV presenter Jimmy Savile was a prolific sex offender over decades.
During the five week trial, the prosecution portrayed Clifford as a master in the art of intimidation and manipulation who used his power and celebrity contacts to prey on girls by promising to introduce them to stars for sex acts.
Clifford denied all charges, saying the allegations against him were "utterly repulsive" lies by fantasists and opportunists out to make money, but admitted to a series of affairs during his marriage to his first wife.
