Barnsley's last-minute equaliser spoiled Jack Grealish's return for Aston Villa and heaped more pressure on their manager Roberto Di Matteo.
Tykes sub Sam Winnall scored with a header following a home corner taken by skipper Conour Hourihane to cancel out Jordan Ayew's opener.
It was Villa's seventh draw in 10 Championship games and rough justice on the impressive Grealish who was recalled after serving a one-match suspension imposed by the club for hosting a rowdy party in a Birmingham city centre hotel – the latest in a growing list of misdemeanours.
Barnsley: Davies: Yiadom, Robertson, MacDonald, Morsy (Armstrong 67), Scowen, Watkins (Hammill 72), Hourihane, Kpekawa, Bradshaw (Winnall 67), Kent
The talented 21-year-old had earlier instigated the move which saw Villa take the lead after 61 minutes.