Dennehy, 31, murdered three men in Cambridgeshire and tried to kill two others in Herefordshire last year.
At Cambridge Crown Court, Gary Stretch, 47, was found guilty of one count of attempted murder and three counts of preventing the lawful burial of a body.
Leslie Layton, 37, was found guilty of perverting the course of justice. The jury is yet to return some verdicts.
The attempted murder conviction for Stretch, of Riseholme, Orton Goldhay, Peterborough, relates to Dennehy's attack on John Rogers in Hereford on 2 April.
The jury of eight women and four men will continue to deliberate on Tuesday. Jurors are still considering verdicts on a further count of attempted murder against Stretch and two counts of preventing the lawful and decent burial of a body against Layton, of Bifield, Orton Goldhay.
Dennehy, of Orton Goldhay in Peterborough, has admitted murdering Lukasz Slaboszewski, 31, Kevin Lee, 48, and John Chapman, 56, in March last year.
The men's bodies were all found in ditches in Cambridgeshire in March and April.
During the trial, prosecutors said Dennehy "cast a spell" over Stretch and Layton and some of her victims as she killed "for fun".
Dennehy was likened to "Uma Thurman from Kill Bill and the woman from the Terminator" by married father of two Mr Lee shortly before his death.
Another victim, John Chapman, had dubbed her the "man woman" because of her intimidating nature. At the height of a nationwide manhunt, she bragged to one witness that she had killed eight people - although no further murders have been detected.
All the murder victims died of multiple stab injuries, including wounds to the heart.
After committing the three murders, Dennehy drove to Hereford with Stretch in a Vauxhall Astra registered in the false company name Undertaker and Sons, the court heard.
Once there Dennehy, a diagnosed psychopath, randomly selected and repeatedly stabbed two dog walkers - Robin Bereza and Mr Rogers - in the street. Both survived despite suffering critical injuries.
Dennehy has also admitted preventing the lawful and decent burial of all three victims and the attempted murders of Mr Bereza and Mr Rogers in Hereford while on the run.
Two men have been found guilty of helping triple killer Joanna Dennehy during her 12-day spree of violence.