Fred Rutten's team dominated the vast majority of the opening Eredivisie fixture of the weekend at De Kuip - even before the visitors had Joey van den Berg sent off on the hour mark.
Yet a frustrated Feyenoord required a 70th-minute leveller from captain Immers to earn a draw after Hakim Ziyech put the 10 men ahead with a wonderful free-kick shortly after Van den Berg's dismissal.
Heerenveen started brightly and had the first attempt on goal when Luciano Slagveer burst past two Feyenoord defenders and shot just wide after three minutes.
That jolted the hosts into life, though, and Rutten's side soon began to control proceedings.
Mitchell te Vrede had Feyenoord's best chance of the first half when his header was well saved by Heerenveen keeper Kristoffer Nordfeldt shortly before the interval.
The second period followed much the same pattern - Feyenoord probing while Heerenveen resisted - and the home team seemed to be given a huge helping hand when Van den Berg was given his marching orders.
Despite that setback, Heerenveen went ahead soon after courtesy of Ziyech's 25-yard set-piece.
However, their lead lasted just three minutes, as Immers climbed highest to convert substitute Ruben Schaken's right-wing cross.
Feyenoord, who announced the loan signing of Bursaspor's Colin Kazim-Richards earlier on Friday, pressed for a winner with Elvis Manu and Tonny Vilhena going closest.
But they could not find a way past an inspired Nordfeldt and had to settle for a point.
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