Conor Wilkinson gave Barnsley an early lead but it was a different story after the break with Jay O’Shea, Sylvan Ebanks-Blake and Sam Morsy completing a deserved victory.
Barnsley went ahead in the fourth minute when Danny Crowley broke from inside his own half to set up Wilkinson, who beat goalkeeper Tommy Lee from 12 yards.
Sam Winnall had a chance to increase Barnsley’s lead in the 19th minute but his shot was too close to Lee and Chesterfield almost equalised when Gboly Ariyibi broke through on the left, but visiting goalkeeper Adam Davies saved at his near post.
Davies turned behind Dan Gardner’s shot but was beaten in the 49th minute when Ebanks-Blake set up O’Shea to score from 15 yards.
Ebanks-Blake fired over in the 62nd minute but made no mistake 10 minutes later when he scored from eight yards when Barnsley had failed to clear a corner and Morsy sealed victory in the 73rd minute with a 20-yard shot that went in off a post.