The 2013 results show the firm, based in Stafford Road, Wallington, has moved up from 13th position last year to number eight this year.
More than 500 small and medium sized companies entered the contest with ratings dependent on judgements made by staff themselves. This year the survey highlighted a number of areas where Penta excelled.
Its work in the community was voted into third place and there were high rankings for the company's apprenticeship scheme and fast track leadership programme.
And there was good news for Penta's founder and chief executive Paul Clark, with 93 per cent of his staff describing him as an inspiring figure who is always developing his own leadership skills and is also considered to be open and honest.
"Our people are at the heart of our business and this is a very special award because it is entirely based on feedback from our staff."
He added: "When we launched Penta 15 years ago, we were determined to create an inspiring working environment where staff were valued, recognised, rewarded and well looked after."