The 20-year-old joined PSV from Vitesse in the summer of 2004, but has failed to break into the first team at the Dutch giants.
Ter Horst has signed a one-year contract at Heracles.
“We have seen him play on several occasions,” said Heracles sporting director Nico Jan Hoogma.
“Olivier is a solid defender who can play both as a centre-back and as a left-back. We will give him the chance to prove his worth at Eredivisie level.”
