The Bears closed the first day on 250-6, having been 238-3 after Nottinghamshire, chasing a fourth successive win, had failed to make the desired early inroads in humid conditions.
Warwickshire captain Will Rhodes led the way for his side with a resolute 91 before falling to the last ball before tea.
Sam Hain (61) and Matt Lamb (43 not out) added 75 in 26 overs in the final session before Paterson’s burst of three wickets in 14 balls evened the day up again.
Runs never flowed freely, but it was a tight, enthralling day’s play amid a lovely atmosphere in the Birmingham sunshine with spectators back in the ground.
There were 1,808 Warwickshire members present and they ended the day happy enough having seen their team find some batting resilience.
Worcestershire batsman Jack Haynes hit his career best score but fell just short of a maiden first-class hundred for the second time this month in the clash with Derbyshire at New Road.
Haynes had struck 87 against Warwickshire at Edgbaston before being run out and yesterday batted in impressive fashion to move to within three runs of reaching his century.
But on 97 the England Under-19 player, who was dropped by wicketkeeper Brooke Guest off Dustin Melton when he was on 10, was caught on the boundary off spinner Matt Critchley to deny him his hundred.
Brett D’Oliveira also produced an excellent knock of 71 as Worcestershire recovered from 62-3 to reach 336-7 by the close.
Wicketkeeper Ben Cox (49) and Ed Barnard (48 not out) scored freely against the second new ball in adding 88 for the seventh-wicket before the former was caught behind in the final over from Ben Aitchison.