The Devon side remain rock bottom after going down to goals by Steven Taylor, Kevin Nolan and Andy Carroll with the only bright spot for the 2,000 loyal Argyle fans making 800-mile round trip being an effort from Karl Duguid.
The win means Newcastle have maintained their 100 per cent home record by making it four wins out of four and are sitting in second place in the Championship behind West Brom who were crushing 5-0 winners at Middlesbrough.
And with Bristol City held at home 1-1 by Scunthorpe, Newcastle are now the only Championship side able to boast that 100 per cent home record.
Newcastle got off to a flyer with a goal after six minutes by crowd favourite Taylor. Geremi swung in a right-footed corner from the left and found the central defender inside the six-yard box.
He scored his second goal of the season with a stopping header that gave Romain Larrieu no chance in the first meeting between these sides in 18 years.
A late 29th-minute challenge on Danny Simpson by Cillian Sheridan saw the Manchester United loan player struggle to shrug off the knock and he was quickly replaced by Ryan Taylor.
Plymouth then enjoyed their best spell when Chris Clark saw a 30-yard free-kick blocked by Joey Barton and, from another free-kick, he fired wide.
Having been a scorer at one end, Taylor came to the rescue late in the first half when a clearance dropped to Sheridan 15 yards from goal and Taylor made a brave block with his body to prevent a certain goal.
St James' Park fell to a deafening silence early in the second half when Duguid's outstretched foot flashed the ball beyond Steve Harper as he became the first visiting player to score on Tyneside this season.
Newcastle made a double substitution after 59 minutes with Nile Ranger replaced Peter Lovenkrands and Danny Guthrie took over from Barton.
And the response was almost immediate with Newcastle going back in front on the hour mark when Nolan, from only six yards out, headed in a cross.
Larrieu then saved from Ranger and did well to keep out a Nolan volley but another United goal seemed inevitable and it came six minutes from time.
The ball broke to Carroll on the edge of the box and the young striker pounced for the second successive match when he side-stepped his marker and lashed the ball across Larrieu.
And Carroll came so close to another in the final minute, his overhead kick smashing against the bar.