John Watson, 35, lay in wait for the victim to leave the house of his ex-wife, with whom the victim was having a relationship with.
He then tied him up, bundled him into his car and stabbed him before eventually he was saved by police.
Watson was convicted by a unanimous jury at Reading Crown Court on Thursday.
The court heard the men became friends while stationed together at Combermere Barracks, near Windsor, last year.
The relationship broke down after the victim started a relationship with Watson's former partner following the breakdown of their respective marriages.
The 28-year-old victim sustained a number of injuries, including a stab wound to his side and left elbow, as well as damage to a tendon in his finger which required surgery.
Watson had already been found guilty of one count of kidnap in relation to the attack, and pleaded guilty to one count of possession of an offensive weapon.
Investigating officer Det Con Lyndsey Shaw said: "This was a callous and premeditated act on the part of John Watson.
"Fortunately the victim did not suffer any long lasting injury and physically he has been able to move on from this ordeal".
Watson is due to be sentenced at the same court on 9 February.
A soldier who abducted and stabbed his comrade and love rival in Windsor has been convicted of attempted murder.