The wicketkeeper shared a sixth-wicket partnership of 141 with Chris Woakes after their side had slipped to 99 for 5 by four o'clock in the afternoon.
The stand took the hosts to within 68 runs of Australia A's first innings score of 308 for 9 declared.
Kieswetter arrived at the crease with England Lions on 46-3 and the hosts were in even more trouble just seven runs later when Eoin Morgan went for 12.
Cue Kieswetter's heroics, assisted first by Ben Stokes who contributed a useful 26, and then by Woakes, who ended the day on 48 not out.
The Somerset man's century came off 116 balls and in 173 minutes, with 16 boundaries and one six.