The 24-year-old central midfielder has played eight of the Reds’ ten Championship matches this season, missing two with injury.
Mowatt played every minute under Stendel last season as Barnsley gained promotion from League One and has the most assists in this campaign, including a corner for Aapo Halme’s opener against Derby County on Wednesday.
Stendel, who is in charge of the one of the youngest squads in the country, said: “We don’t have that many leaders in our team. But when you see Alex Mowatt on the pitch, he is not a big talker but he works for 11 players and shows he is a leader. He is attacking, defending and fighting for the team.
"More players need to understand that they can play like Alex. We need time but it is easier to develop leadership when you win games.”