The reading was the highest since April 2011 and marked the eleventh consecutive month over the 50-point threshold dividing an expansion in activity from a contraction.
New contracts predominately came from the domestic market, although exports remained strong, if down on July's near-record high.
The latest PMI business survey showed both the output and new orders sub-indexes nudged back into expansionary territory, pushing the pace of hiring to the highest in nearly 4-1/2 years.
The latest figure signaled the third successive improvement in Greek manufacturing sector conditions, and the sharpest since August 2008.
The Commerce Department raised its estimate of second-quarter GDP growth to an annual rate of 3% from 2.6% previously, beating economists' forecasts of 2.8%.
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"The manufacturing sector appears to be on track to contribute towards an upswing in GDP growth in 2017", IHS Markit economist Sam Teague, said.
The rate of growth was little changed from July's five-month high.
"The rebound in August, led by the consumer goods, intermediate and capital goods sectors, suggests that manufacturing firms are now adjusting to the GST regime and that business is returning to normal", it added.
"Production and employment lifted and new orders grew strongly in a month of broad-based expansion across the sector".
However, stricter environmental policies were a key factor leading to longer delivery times, whilst inflationary pressures intensified as input costs and output charges both rose at faster rates.
"Companies linked gains in new export work to increased business from mainland Europe, the USA, China and Australia". The rate of job creation was the highest in three years. Manufacturers' selling prices rose at a solid, yet slower, pace.