There appeared nothing on when Johnson received the ball 25 yards out but he spun and drilled a low shot through bodies on the edge of the area and into the corner.
That goal ended hopes of a sixth-successive league win to match our best run since 1990 - that mark looked on when Defoe crashed home his 15th goal of the season in all competitions off the post after 54 minutes.
However, Johnson's moment arrived with 78 minutes on the clock and it would be difficult to say Palace didn't deserve something looking at the whole 90 minutes.
The first half was uncannily similar to the Boxing Day clash at Norwich with possession equal but Palace creating the better chances.
The visitors started at a cracking pace and had a goal disallowed as early as eight minutes, Johnson tapping in after Robinson palmed out a Lakis dipper but four players were offside as we pushed out.
King was at his best to slide the ball away from the breaking Soares before we responded with efforts from Ricketts, Kanoute and Carrick.
Robinson vitally touched away a Lakis cross heading for Johnson while Kiraly was forced into his only diving save of the half, low to his near post to deny Kanoute.
Defoe and Kanoute tried their luck again before a flurry of action at the other end.
Lakis should have done better from 15 yards and Riihilahti was twice left free to meet corners, neither header seriously troubled Robinson.
Then the chance and save of the half. Lakis was involved again down the left, his low cross found Johnson six yards out, it looked like he had to score but his prod allowed Robinson to keep the ball out. Routledge made a hash of the rebound but it fell kindly for the supporting Riihilahti only for him to knee the loose ball over from six yards.
The second half was a different story. With Mendes on for Ricketts at the interval, it took just a minute to signal out intent, Brown firing in a shot from 22 yards that Kiraly did well to hold.
The Palace goal was peppered from about that range for the next 25 minutes.
Defoe's snapshot was tipped onto the post by Kiraly before the breakthrough a minute later with 54 minutes on the clock, Defoe controlling Edman's pass, cutting inside Hughes and lashing home off the post.
Kanoute was inches offside as he rolled home a disallowed second goal before testing Kiraly again from 20 yards and then Defoe took over, three times cutting in from the left before shooting at Kiraly, all three taken by the Palace keeper.
It looked like a second goal had to come at this stage although Palace were by no means out of it - a couple of penalty appeals kept the defence on their toes and then the unthinkable.
With 12 minutes left, Johnson picked the ball up 25 yards out, almost with his back to goal, nothing on, but managed to turn and drill the ball through a couple of bodies past an unsighted Robinson into the bottom corner. It was greeted by an almost stunned silence from another packed home crowd.
Head Coach Martin Jol threw on Robbie Keane in an attempt to get the win back but the closest we came was in the final minute when Defoe's effort deflected inches wide with Kiraly beaten.
GUIDE TO THE ACTION
1min: Butterfield did well down right flank, held off Ziegler and crossed dangerously from byline, ball drifted over Robinson and attacking Soares and put out for corner.
3mins: Johnson weak effort after winning possession 20 yards out.
6mins: Defoe fed ball into Ziegler, low strike deflected just wide.
8mins: GOAL DISALLOWED. Lakis dipper from 22 yards palmed out by Robinson, Johnson tapped in rebound but four Palace players offside.
10mins: Soares threatened to break through but brilliant saving tackle from King.
14mins: Ricketts volley from 25 yards deflected wide. From Ziegler's corner, Kanoute flick at near post just too far away from Gardner.
20mins: Carrick dragged shot wide under pressure from 25 yards.
24mins: SAVE. Robinson vital touch to Lakis low, driven cross to divert ball away from Johnson and Soares.
27mins: SAVE. Break from Palace attack, Brown into Kanoute, low shot to near post tipped wide by Kiraly.
28mins: Defoe shot blocked and deflected into Kiraly's hands.
30mins: Kanoute took Carrick's pass superbly on his chest, turned away from Hall and cracked a shot that Kiraly had to take at second attempt.
35mins: CHANCE. Pamarot committed to challenge, Soares poked ball away for Lakis, now free, cut inside but made hash of shot from 15 yards.
35mins: Riihilahti free header from 16 yards from Routledge's corner but couldn't keep on target.
38mins: CHANCE. Riihilahti there again, this time from Hughes corner, but headed straight at Robinson.
40mins: SAVE/MISS: Lakis cross from right found its way to Johnson, six yards out, Robinson somehow managed to keep out toe poke, Routledge made complete hash of follow up volley and Riihilahti kneed loose ball over from six yards.
43mins: Palace break from our free-kick, Routledge's pace took him away from Edman, one-two with Butterfield before firing over.
Half-time: Spurs 0, Palace 0
Half-time: SUB. Mendes for Ricketts.
46mins: SAVE. Measured pass into Kanoute from Ziegler, he picked out Brown who held off one challenge before drilling a left-foot shot from 22 yards that Kiraly did well to hold low to his left.
53mins: WOODWORK. Defoe shot out of nothing from 22 yards tipped onto post by Kiraly.
54mins: GOAL. Defoe controlled lobbed pass from Edman, turned away from Hughes and crashed shot in off the post from 20 yards.
Spurs 1, Palace 0
60mins: GOAL DISALLOWED. Defoe fed ball into Kanoute who finished well, goal rightly ruled out for offside.
64mins: Mendes won ball centrally, into Defoe, snapshot from 25 yards straight at Kiraly.
64mins: Kanoute picked up ball wide left, cut in, left-foot shot straight at Kiraly.
66mins: Diagonal pass from Mendes to Defoe, cut inside Hall, Kiraly had to take fierce shot at second attempt.
67mins: SUB. Torghelle for Routledge.
70mins: PENALTY? Appeals from Palace as Torghelle went down under pressure from Gardner, nothing there.
71mins: Defoe, drifting out left more and more, picked up ball in same position again, cut inside Hall, shot deflected into Kiraly's hands.
77mins: YELLOW. Pamarot for foul on Lakis.
78mins: GOAL. Goal out of nothing from Johnson, spun on ball 25 yards out, shot went through bodies and crept in at far post.
Spurs 1, Palace 1
82mins: SUB. Keane for Kanoute.
88mins: Keane inches away from Brown's deflected cross.
89mins: CLOSE. Brown won ball in midfield, prodded ball through to Defoe, shot from 18 yards deflected inches wide. From corner, ball came out to Edman who drilled a yard over.
Final score: Spurs 1, Palace 1
Line-ups: Spurs (4-4-2): Robinson; Pamarot, Gardner, King, Edman; Ricketts (Mendes, 45), Carrick, Brown, Ziegler; Kanoute (Keane, 82), Defoe. Subs: Fulop, Redknapp, Davenport.
Crystal Palace: Kiraly, Butterfield, Granville, Routledge (Torghelle, 67), Johnson, Riihilahti, Hughes, Soares, Hall, Sorondo, Lakis. Subs: Speroni, Leigertwood, Boyce, Andrews.
Referee: Uriah Rennie.
Andy Johnson's goal out of nothing stunned the Lane, cancelled out Jermain Defoe's opener and ended our winning run in the Barclays Premiership on Tuesday.