Gary Stretch has been found guilty of three counts of preventing the lawful burial of a body and one of attempted murder at Cambridge Crown Court.
Leslie Layton was also found guilty of perverting the course of justice.
Dennehy, 31, of Peterborough, has already admitted the murders of Lukasz Slaboszewski, 31, Kevin Lee, 48, and John Chapman, 56, in and around Peterborough over 10 days last March.
She also admitted preventing the lawful and decent burial of all three victims and two charges of attempted murder.
Stretch's attempted murder conviction relates to Dennehy's attack on John Rogers on April 2. The jury will continue to consider its verdict in relation to his involvement in the attempted murder of Robin Bereza on the same day.
Layton is accused of preventing the lawful burial of Mr Chapman and Mr Lee but the jury is yet to reach a verdict on those counts.
The convictions follow 31-year-old Dennehy's killing spree in March last year.
Afterwards she drove to Hereford with Stretch in a Vauxhall Astra registered in the false company name Undertaker and Sons.
Once there the diagnosed psychopath randomly selected and repeatedly stabbed two dog walkers - Mr Bereza and Mr Rogers - in the street.
Both survived despite suffering critical injuries.
A third man,Robert Moore, 55, of Belvoir Way, Peterborough, is awaiting sentence after admitting assisting an offender.