It is believed the defensive midfielder’s transfer, tipped to be worth around £340,000 (A$600,000), to the Tykes from Sparta Rotterdam will be announced on Friday (UK time).
Brisbane-born and raised Dougall has spent the past three seasons with Sparta in the Netherlands, after one year with Telstar.
The 25-year-old helped the Castle Lords get promoted to the Eredivisie in 2016, but Sparta finished 17th and were relegated to the Eerste Divisie at the end of last season.
Dougall, who can play in both midfield and defence, made 81 first-team appearances for Sparta, who were also home to three-capped Socceroo Craig Goodwin before he returned to Adelaide United for the upcoming A-League season.
In 2015, Dougall made his debut for Australia at Under-23 level, earning four caps for the Olyroos.
The Queenslander started his career as a 16-year-old with two years with the Queensland Academy of Sport and then had four years with Brisbane Roar’s National Youth League team, but never made it through to the A-League.
Dougall left the Roar in 2013 and spent a season with Brisbane City in the NPL Queensland and banged in 10 goals in 34 matches before heading to Holland.
Barnsley were relegated to League One after finishing 22nd of 24 teams in the Championship.
The south Yorkshire outfit, who were bought by new owners in December, appointed former Hannover 96 coach Daniel Stendel as their new manager in June.
A number of Australian players have appeared for Barnsley over the years, including Ryan Williams, Jacob Burns, Callum Elder, Kyle Nix and David Scarsella.