Zak Chappell starred on the first day at The County Ground taking his best Derbyshire figures, as the home side dominated Glamorgan.
The fast bowler took 6 for 47 as the visitors were bowled out for 168, Timm van der Gugten top scoring with an unbeaten 46.
Glamorgan were 32 for 6 before Dan Douthwaite (36) and van der Gugten led a mini recovery, but Derbyshire closed on 119 for 2 with Harry Came not out 58.
It leaves them in a strong position to push for a first championship victory at The County Ground since they beat Sussex in August 2019.
On a morning more in keeping with October, Derbyshire’s decision to bowl first on a grassy pitch paid immediate dividends with three wickets falling in the first five overs.
In blustery conditions, Glamorgan’s top order had no answer to Chappell’s relentless accuracy and Luis Reece’s swing as they slumped to 9 for 3.
Ben Kellaway’s promotion to opener was short-lived and he followed a pair on his first-class debut last September by edging a ball from Chappell that moved away late to register another duck in his third red ball innings.
In fairness, his more experienced team mates fared little better with Billy Root bowled by a Reece delivery that kept low before Sam Northeast pushed forward to Chappell and was caught at second slip.
Kiran Carlson played across one from Chappell that appeared to be going down before Reece got some late swing to have Colin Ingram caught behind.
When Chris Cooke was caught behind down the legside off one of the few bad balls Chappell bowled, Glamorgan were in disarray and grateful for the rain which resulted in an early lunch.
Chappell, who passed 50 wickets in all formats for the season, left the field with outstanding figures of 4 for 9 from 6.4 overs but after the resumption they were dented when Douthwaite hit him for three fours in an over.
With van der Gutgen playing solidly, the pair added 55 from 97 balls in relative comfort before Pat Brown removed Douthwaite with a snorter that nipped away late to take off stump.
Chappell celebrated his fifth wicket when Mason Crane fenced at one to give Brooke Guest his fourth catch but Fraser Sheat on his debut looked capable until he top edged a pull to mid-wicket.
Ned Leonard marked the first match of his loan spell from Somerset by helping van der Gugten take Glamorgan past 150 and drove Jack Morley’s second ball for six before he tried again next ball and holed out to long on.
Van der Gugten matched Chappell’s discipline with a probing spell but Sheat and Leonard could not exert the same pressure.
Reece and Came shared an unbroken treble century stand against Glamorgan last season but this time they managed only 21 before Reece was defeated by a full length ball from van der Gugten.
Guest played a loose stroke, clipping Leonard to mid-wicket with the score on 41 and Came should have gone on 28 but Ingram at first slip dropped an edge off Leonard.
Came took advantage, seizing on any width to reach an 84 ball 50 which contained 10 fours and with Wayne Madsen motoring to an unbeaten 41, they added 78 before bad light ended play.
