Lewis had gone 13 games without a point before picking up two assists Tuesday night in the Kings' 3-1 win over Edmonton.
His game-winning goal on Wednesday came at 15:20 of the first period on a play in which the 26-year-old showed great poise.
Lewis collected a rebound at the side of the night, paused briefly, then zipped a shot into the top corner over Flames goaltender Joey MacDonald's shoulder for his first goal in 31 games going back to last season.
That would be all the offense Jonathan Bernier needed. With Jonathan Quick getting
Dustin Brown and Jeff Carter also scored for Los Angeles. The defending Stanley Cup champions wrap up a grueling stretch in which they played eight of nine games on the road.
T.J. Brodie scored for Calgary.
The Flames have two days off before returning to action Saturday against Minnesota.
Flames captain Jarome Iginla made a nice setup on Brodie's tying goal at 14:51 of the first, finding him sneaking in from the blue line where the defenseman moved his way through the slot and put a quick shot inside the post.
The game was tied for just 29 seconds before Lewis put the Kings ahead for good.
Los Angeles added a goal halfway
It was Carter's team-leading eighth goal, all coming in the past 13 games.
With Miikka Kiprusoff (knee) missing his eighth game, MacDonald made his second start and first at home since being claimed off waivers from the Detroit Red Wings.
MacDonald was in good form in the second period as the Kings outshot
MacDonald finished the game with 30 saves.
Los Angeles was playing its second game in as many nights, but it did not look tired as they went on the attack from the opening faceoff. Brown fired a shot into the top corner at 6:15, giving the Kings a 1-0 lead.
Calgary entered the night with the NHL's third-ranked power play, but it was unable to capitalize on four opportunities.
Notes: Iginla has one goal in 15 games this year and two in his past 25 dating back to last season. ... Iginla's assist was career point No. 1,083, moving him within five points of Theoren Fleury for 59th on the NHL's all-time list. ... Kings defenseman Rob Scuderi had two assists, matching his career high for points in a game. The veteran of 552 career games had two points four previous times. ... The Kings play 13 of their next 16 games at home.