The rate of cases per 100,000 is now 30.8, after it fell to a low of 8.5 per 100,000 in the last week of August.
The sharp rise makes Barnsley the ninth most-affected area in Yorkshire - higher than Rotherham, which has a rate of 23.4 per 100,000, but significantly lower than Bradford and Leeds which have both been threatened with local lockdowns.
There have been 2,213 cases in Barnsley up to September 9, with 76 cases in the week commencing August 31 - a rise of 56 on the prior week’s figures.
The increase has mostly been seen in younger people, according to Barnsley Council public health director Julia Burrows, with fewer severe cases and hospitalisations due to Covid-19 seen in recent weeks.
“However, there remains a real risk of this rise generating wider spread including into more vulnerable groups of people (such as the elderly or those with underlying disease) and we are starting to see signs of this in other parts of the country and in Europe,” said Ms Burrows.
“Adhering to the guidance, keeping transmission down and supporting people at greater risk remains very important.
“As per the national trend, the increase in Barnsley is largely in children and young people and not associated with severe illness.
“We continue to monitor this closely and to support schools and other educational and workplaces to control spread.”