If not for Johnson's play in the final minute, the Hawks' lack of concentration could have been costly.
Johnson scored a season-high 36 points, including two free throws with 0.6 seconds remaining, and the Hawks recovered after trailing most of the game to beat the Kings 100-98 on Monday.
"The first three quarters our defense was pretty much nonexistent," Johnson said. "In the fourth quarter we were able to make some stops."
The Hawks play at Miami on Tuesday.
"You get to measure yourself against one of the top teams in the East," Johnson said. "I'd be lying if I said it was just another game."
Hawks coach Larry Drew said he was relieved "especially now that we have to go down to Miami.
"This could have been a very bad loss going to Miami."
Johnson drove past three defenders for a layup with 23 seconds remaining to give Atlanta a 98-96 lead. Carl Landry answered with a tying basket for Sacramento with 11.7 seconds remaining.
Following a timeout, Johnson was fouled by Tyreke Evans on a drive with less than a second remaining. Johnson made both free throws.
The Kings, last in the Western Conference, fell to 3-15 on the road despite outplaying the Hawks most of the game.
"We get 'em 47-38 on the boards, get nine more field-goal attempts (92-83), we only had seven turnovers for the game, it's just a shame," Kings coach Paul Westphal said. "We played hard, we played well against a really good team at the end of a six-game road trip and just came up that short."
The Kings were 1-5 on the road trip.
Landry's layup with 36 seconds remaining tied the score at 96-all before Johnson took over for the Hawks.
"He was Joe today," Drew said. "You could see he had that bounce in his step. He wasn't hesitating in his shot.
"That's Joe, but we cannot come out every night and expect Joe or even hope for Joe to bail us out."
Johnson made 16 of 27 shots from the field and added six assists.
"We tried everything throughout the game," Westphal said of the team's efforts to defend Johnson. "He was magnificent."
The Kings didn't trail until going scoreless for 4½ minutes as Atlanta scored 13 unanswered points as part of a 20-4 run to open the fourth quarter.
"For three quarters, we didn't give that team the respect we should give every team we play," Drew said.
Johnson's jumper pulled the Hawks even at 86-all for the first tie since late in the first quarter. Horford blocked Evans' shot and then scored on a baseline jumper to give the Hawks their first lead at 88-86.
The Kings had four scorers in double figures when they led 62-53 at halftime.
Sacramento set a season high by scoring 70 points in the first half on Saturday at Detroit, but had only 36 points in the second half of a 110-106 loss. The Kings repeated that formula by again scoring only 36 points in the second half after their high-scoring start against Atlanta.
"We play hard," Evans said. "We've just got to find a way to put away that type of game. We always start out good, then we let it kind of slip away. We fight to the end of the game, we've got to learn how to close out games."
Horford set a career high by blocking seven shots.
Farris Watkins, the great-niece of Rev. Martin Luther King Jr., sang the national anthem. The Hawks also had a halftime ceremony honoring King, who was an Atlanta native, on his annual memorial day. ... Kings F Francisco Garcia (sore left calf) did not play. G-F Donte Greene was the fill-in starter and led the Kings with 11 rebounds. ... Hawks F Marvin Williams missed his eighth straight game with a lower back injury. ... The Kings' last win in Atlanta was on Feb. 20, 2008.