After six years in charge, Arrasate will step down at the end of the season.
He said, "I have made the decision not to renew with Osasuna.
"It is difficult to be happy and give your best if you are not convinced. It is the most beautiful stage of my life.
"I don't know the legacy I leave, but Osasuna will always be marked in my heart."
Arrasate added: "I leave super calm, proud and at peace with myself, and that is worth a lot to me.
"I leave a door open for a return."