JLR officials said the takeover would help it boost its client services across the mining, industrial, energy and forestry sectors in northern Ontario, as well as expand its existing team in Timmins.
"This represents a significant business development and technical growth opportunity for us all," JLR president and CEO Guy Cormier said.
"Where once stood two competitors now stands a stronger, more dynamic and unified front."
PES co-founder Brian Emblin added: "This is a very positive and exciting time for us."
A timeline for the combination of companies was not released.
PES, which has a specialisation in brownfield mining, was established in 2004.
JLR, which offers engineering, architecture, planning and project management services, has seven offices in the Ontario province.