Byfield one-timed a pass from Drew Doughty at the right face-off dot to give the Kings the win.
Warren Foegele, Kevin Fiala and Alex Laferriere scored and Darcy Kuemper made 12 saves for the Kings (9-5-4), who have won three in a row and four of their past five.
John Tavares scored twice and Bobby McMann scored for the Maple Leafs (8-8-2), who are 0-3-1 in their past four. Dennis Hildeby, who appeared in his fourth straight game since being recalled on Saturday, made 33 saves.
Toronto was without captain Auston Matthews, who is out a week with a lower-body injury sustained in a 5-3 loss to the Boston Bruins on Tuesday. They are 45-24-3 all time without Matthews in the lineup since he entered the League in 2016-17.
The Maple Leafs went up 1-0 at 8:06 of the first period. McMann turned the puck over to Adrian Kempe in the defensive zone but stole it back, leading to a breakaway where his shot caught a piece of Kuemper’s right pad before trickling over the goal line.
Tavares made it 2-0 at 16:39 when he redirected a pass from Oliver Ekman-Larsson at the top of the goal crease.
Foegele cut it to 2-1 at 6:51 of the second period when he shot low to the glove side from the left face-off dot.
The Kings tied it 2-2 at 15:41 when Fiala put in a rebound at the side of the net from Byfield’s shot.
Tavares put Toronto up 3-2 at 17:16 when he got behind the Kings defense in the slot, took a pass from Nylander, who was high in the slot, and deked to the backhand past Kuemper’s outstretched left pad.
Laferriere tied it 3-3 at 13:10 of the third period when he deflected a point shot from Brandt Clarke in the slot.