The Calgary-based oil company's head count now stands at 1,600, down from 2,150 at the start of 2013.
Since the fall of 2012, Penn West has reduced its staff by 30 per cent.
The company expects to take a $25-million charge in the third quarter in connection with the layoffs.
"This week, Penn West has taken another series of focused steps to restore its competitiveness," CEO Dave Roberts said in a release.
"These are never easy decisions and parting with such a large number of our colleagues is difficult. The spirit of the company remains positive, and we are focused on stewarding Penn West toward achieving consistent, industry-leading metrics in the areas in which we operate."
Penn West has seen a great deal of upheaval this year. In May, former Suncor Energy Inc. (TSX:SU) CEO Rick George was appointed the company's new board chairman.
A month later, Penn West announced Roberts, a former Marathon Oil executive, would become its new CEO, replacing Murray Nunns. At the same time, the company warned job cuts would be coming and that it would be reducing its quarterly dividend by half.
Shares in Penn West, which reported the job cuts after markets closed, were up 14 cents at $11.92 Thursday on the Toronto Stock Exchange.