Ghana striker Tagoe, who joined Partizan on loan from Bundesliga side Hoffenheim during the winter break, scored his third goal in as many games against Red Star to send the league leaders three points clear of their bitter foes.
Partizan have 62 points with six games left, Red Star are on 59 and third-placed Vojvodina Novi Sad are six points off the pace after a 1-0 setback at OFK Belgrade.
With the north tier of Partizan's stadium empty after Red Star's die-hard fans boycotted the derby because it was played on Easter weekend, the home side had all the support from the 25,000 fans in the terraces.
But it was the visitors who dominated a lively first half and almost took a first-minute lead, when Partizan defender Stefan Savic headed a teasing cross from the left against his own crossbar.
Aleksandar Jevtic headed over the bar for Red Star from close range and his strike partner Andrija Kaludjerovic missed the best chance in the first half, when Partizan keeper Vladimir Stojkovic denied him with a reflex save.
Partizan were confined to several half-chances, the best falling to Tagoe and Stefan Babovic, who scuffed his shot wide from eight metres after a flowing move.
The game appeared to fizz out in the second half before a quick move down the left flank left Tagoe with plenty of work to do, but the striker turned his marker with some ease and then buried his shot into the roof of the net from a tight angle.
A constant threat up front with his pace and running off the ball, the Ghanaian sent the home fans into raptures with his eighth goal in 10 games for Partizan, stretching Red Star's winless league record at their neighbours to three years.
"I have to congratulate Partizan because they wanted it more, while we can only rue the chances we missed in the first half," said Red Star coach Robert Prosinecki who won the European Cup with the club in 1991.
"Not having our faithful in the north tier was a blow but I don't think it was the decisive factor."
His Partizan opposite number Aleksandar Stanojevic said the champions should not take the title for granted.
"We are in a commanding position now but the title race is not over and we have to stay focused so that we cross the finish line first," he said.
"It was an excellent derby and a tremendous first half, many people expected us to falter in the derby after letting Red Star back into the title race with several slip-ups but the players showed character and resilience."
