The Pakistani leg spinner claimed four wickets and then smashed 31 off 17 balls, including four sixes.
He led a rearguard effort after Town had been reduced to 49-5 but Bilal Anjam’s men were eventually dismissed for 144.
Town had earlier restricted the hosts to 175 all out with Mir taking 4-48 and James Stuart, Robert Heyes and Anjam all collecting two wickets apiece.
Rhys Mann dug in for 21 but Doncaster found runs hard to come by and, despite the best efforts of Mir and tailender Heyes (21), the visitors came up short in their first game in the newly-formed Yorkshire Cricket Southern Premier League.
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Elsewhere in the Premier Division, Tickhill put 229-5 on the board at Treeton but the hosts knocked them off with 2.4 overs to spare.
Openers Ross Diver (42) and Mark Cummins (32) laid a solid foundation and Joe Billings then struck 80 off 54 balls to seemingly put Tickhill in the driving seat.
However, the home side had other ideas as Stephen Foster made 60 and Liam Johnson struck an unbeaten 73 to guide his side to an impressive six wicket win.
Town travel to Barnsley on Saturday, while Tickhill host Whitley Hall.