The England-born Nigerians put Paul Warne's men in front on two occasions but the visitors had other plans.
In the 11th minute, Ajayi got the curtain raiser for the Millers but a few minutes later, Joe Lolley restored parity for the Terriers.
Adeyemi, 25, gave the New York Stadium outfit the lead, again, in the 71st minute but Elias Kachunga equalised with Tom Smith’s goal on the stroke of full-time won the maximum points for Huddersfield.
While Ajayi’s first half effort was his first goal for the Terriers, Adeyemi has registered four in 19 league appearances for the bottom placed side.
They travel to Wales to take on Cardiff City in their next English second division encounter on February 18.