Palace should have taken an early lead when they were awarded a penalty after Mousa Dembele had brought down Marouane Chamakh, but Jason Puncheon ballooned the resulting spot-kick way over the bar.
First-half chances were few-and-far-between for the hosts, with Nabil Bentaleb's crossbar-rattling-strike the closest they came to opening the scoring before Eriksen broke the deadlock just after the break.
The 21-year-old raced onto Emmanuel Adebayor's flick-on and duly slammed past a helpless Julian Speroni into the roof of the net.
A day after confirmation that Defoe will be joining Toronto FC at the end of February, the second-half substitute then made it two with a cool finish after being played in by Aaron Lennon.
Tim Sherwood named an unchanged side from the one which suffered a 2-0 FA Cup defeat at Arsenal, with 19-year-old Bentaleb keeping his place in midfield to make his Premier League debut.
Meanwhile, for Palace, Tony Pulis made five changes from the team that were 2-0 winners away to West Brom, with Joel Ward, Mile Jedinak, Cameron Jerome, Chamakh and Puncheon all returning.
The visitors started brightly as Puncheon dragged a shot wide following exchanges between Chamakh and Yannick Bolasie on the edge of the area, before Bentaleb tested Speroni from distance at the opposite end.
Spurs looked vulnerable at the back and Palace were awarded an early chance to take the lead when Michael Oliver pointed to the spot after Chamakh was clumsily bundled over in the area by Dembele.
Puncheon was the man who stepped up, but he got it all wrong with a kick more suited to rugby union than football, horribly skewing his effort high and wide of Hugo Lloris' goalposts.
Pulis' side were causing a number of early problems and Chamakh headed over from a corner before Jonathan Parr saw his shot deflected behind after Puncheon's cross found its way to him at the back post.
Jerome then latched onto Chamakh's flick-on to force a save out of Lloris on the half-volley, before Puncheon and Jedinak both came close.
First-half chances were sparse for the hosts, but they came the closest to opening the scoring when Bentaleb struck the underside of the bar from Dembele's lay-off, with the ball inches away from bouncing over the line.
Sherwood's men came out from the break full of intent as Eriksen saw his effort blocked by Damien Delaney after smart play from Roberto Soldado, but minutes later, the Denmark international was able to open the scoring.
Kyle Naughton, who replaced the injured Kyle Walker, found Adebayor with a long-ball forward, the striker flicked into the path of Eriksen and he lashed home into the roof of the net for his third Premier League goal of the season.
Palace still posed a threat and Jerome gave the Spurs defence a reminder of that when he slammed into the side-netting from a tight angle.
Toronto-bound striker Defoe replaced Soldado on the hour mark to a rapturous ovation from the home crowd and, almost immediately, he fired just wide after wriggling himself into space in the area.
Defoe then doubled Tottenham's lead with a smart finish after good work from Lennon.
There was a slight hint of fortune as Parr failed to clear Lennon's initial ball, but Defoe made no mistake, adjusting his feet before guiding it above the onrushing Speroni.
Chamakh was then denied by Lloris with a smart save before heading over in stoppage-time, but Spurs soaked up the late pressure to climb up to fifth.