The young Magpies trailed in the early stages at the Proctor Cars Stadium, home of non-league outfit Matlock Town, following Lennon Wheeldon's deflected strike.
United's youngsters dominated large parts of the contest, with Magpies skipper Cathal Heffernan hitting the post, but were unable to find an all-important equaliser and were, ultimately, edged out by their Rams counterparts.
Three changes were made from the side which claimed a 1-0 win against Tottenham Hotspur last weekend as Alex Murphy, who made his Premier League debut in a 4-1 win against Chelsea in November 2023, was handed a start for the visitors as well as teenage midfield duo Ellis Stanton and Travis Hernes.
Jay Turner-Cooke, who made his first-team debut for the Magpies' first-team during friendly clash against Al Hilal in December 2022, created the opening goalscoring opportunity of the contest as the 20-year-old attacking midfielder latched onto Anthony Munda's deflected pass but his first-time effort bended over the crossbar.
In the tenth minute, Newcastle fell behind through Wheeldon's strike as the Rams striker raced in behind the United defence before his attempt at goal took an unfortunate deflection before the ball looped over Magpies goalkeeper Aidan Harris.
Leo Shahar, who received an international call-up with England Under-18s, was unable to net his first goal at under-21 level as the teenage right-back's free kick from the edge of the box was held by Derby shot-stopper Jack Thompson.
Harris, who signed his first professional contract with his boyhood club last month, produced a key stop to prevent Cruz Allen doubling the hosts' lead, beating away the forward's powerful drive from distance.
In the second-half, Turner-Cooke went close to drawing the young Magpies level as the South Shields-born youngster raced onto Stanton's pass before his resulting effort was drilled into Thompson's gloves.
Heffernan, who made his Magpies first-team debut during a 4-1 win against Urawa Red Diamonds last month, struck the post towards the hour mark as the Irish centre-back's deft header from Shahar's lofted free-kick kissed the outside of the woodwork before Thompson collected the loose ball.
Harris stopped Wheeldon doubling his and Derby's lead as the Rams striker advanced into the penalty area but his low shot at goal was crucially parried by the 17-year-old shot-stopper before the ball was cleared from the penalty area.
Turner-Cooke almost levelled the clash in the closing stages but the winger's free-kick from the edge of the box took a slight deflection before brushing the side-netting.
James Huntley, introduced from the substitutes' bench in the second-half, almost equalised in stoppage-time as the Ashington-born midfielder latched onto Charlie McArthur's cross from the left flank before his volley was saved from point-blank range by Thompson.
Newcastle United Under-21s turn their attention to EFL Trophy action on Tuesday, 3rd September when facing League Two Bradford City at Valley Parade in their opening Northern Section Group H clash (kick-off 7.30pm BST).
Newcastle United Under-21s: Aidan Harris, Leo Shahar, Cathal Heffernan (c), Ciaran Thompson, Alex Murphy (Charlie McArthur 59), Ellis Stanton (James Huntley 59), Anthony Munda, Travis Hernes (Alfie Harrison 84), Jay Turner-Cooke, Trevan Sanusi, Ben Parkinson (Josh Donaldson 84).
Subs not used: Adam Harrison.
