The County were in control of the contest after Notts started the day on 38-4 in reply to the hosts’ 260 in the first innings.
But Michael Lumb struck 99 and shared crucial stands with former Northants man Riki Wessels (71) and Chris Read (59) as Notts battled back to close on 384-8 - a lead of 124.
Their effort was further enhanced after tea with Ajmal Shahzad finishing the day unbeaten on 65 while Luke Fletcher struck 49.
Kyle Coetzer picked up the wicket of Lumb, who edged through to wicketkeeper Adam Rossington while Mohammad Azharullah bowled Wessels for what was the first wicket of the day.
Andrew Hall trapped read lbw while James Middlebrook was responsible for the dismissal of Fletcher just before the close.
Shahzad and Andre Adams will resume in the middle on Sunday morning when Nottinghamshire will look to strengthen their position further.