The 7-footer came through in a 97-93 victory over the Chicago Bulls on Saturday night.
Bynum made the go-ahead basket with 3:35 left and had his best all-around game of the season with 20 points, five blocked shots and 10 rebounds in 30 minutes.
"It felt good," Bynum said. "I won't lie to you."
Bynum said earlier in the season he was contemplating retirement as he attempts a comeback from surgery on both knees. The injuries sidelined him for all of last season in Philadelphia and he admitted he was only a shell of himself on the court.
"Tonight we saw a little bit of what Andrew is capable of bringing to the table," Cavaliers coach Mike Brown said.
Bynum hopes Saturday's performance is a sign of something positive for himself and the team.
"I was able to have a little more bounce, a little more jumping ability," he said. "I hope my knees feel good after this."
Bynum and Dion Waiters each scored 20 points, and the Cavaliers held off a late rally by Chicago. Cleveland, which had lost five straight and eight of nine, built a 12-point lead in fourth quarter, but the Bulls rallied for an 88-87 edge on Tony Snell's basket with 3:59 remaining.
Bynum, who was 8 of 14 from the field, hit a 5-footer to put Cleveland ahead for good and Kyrie Irving scored after stealing the ball from Kirk Hinrich. Waiters converted another turnover into a layup to put the Cavaliers ahead 93-88 with 2:09 to play.
Waiters scored again to give Cleveland a seven-point lead, but Luol Deng's 3-pointer cut the lead to 95-91.
Carlos Boozer's basket with 40 seconds left trimmed it to 95-93. Following a miss by Bynum, the Bulls called timeout with 17 seconds remaining. Deng drove to the basket but his shot rolled off the rim and the Bulls missed three tip-in attempts.
Tristan Thompson grabbed the rebound and made two free throws with 9 seconds remaining sealed the win.
Irving, who added 19 points for Cleveland, knows how important Bynum can be to the team.
"When you have someone you can throw it down to, you know he can get his shot when he wants," Irving said. "He draws so much attention. It opens up a lot of opportunities for all of us."
Deng scored 27 points for the Bulls, who finished 1-5 on their road trip in which they lost point guard Derrick Rose for the season with a knee injury.
"This was the end of a long trip," Bulls coach Tom Thibodeau said. "We've got to gather ourselves quickly now because we don't have much time before we play again."
The Bulls played their fourth game without Rose, who had surgery for a torn meniscus in his right knee last week after getting hurt Nov. 22 in Portland.
Chicago also was blown out by 39 points by the Los Angeles Clippers and lost in overtime to Utah during the trip. The Bulls ended a four-game losing streak with Friday's 99-79 win at Detroit.
"We learned a lot on the road, but we've got to do better," said forward Taj Gibson. "Just because we're coming home doesn't mean anything. Teams tend to get a chip on their shoulder when they come into Chicago, so we have to be ready."
Cleveland led by five points at halftime, but started the third period with a 15-5 run to lead 71-56 midway through the quarter.
Chicago had won 12 of its last 13 games against Cleveland, including a 96-81 home victory on Nov. 11, but the Cavaliers scored the game's first seven points, forcing Thibodeau to use a 20-second timeout at the 10:38 mark. The Cavaliers scored 27 points and were 11 of 18 from the field in the first quarter after being held to 10 points in the opening period Friday in a 103-86 loss at Boston.
Snell and Gibson each scored 18 points for Chicago.
Bynum blocked consecutive shots on the same possession by Joakim Noah in the first quarter. ... Thibodeau was given a technical foul by official Nick Buchert in the second quarter. ... Cavaliers G C.J. Miles, who missed four games with a pulled right calf, returned to Cleveland's starting lineup and scored six points. ... Cleveland F Earl Clark (flu) was inactive. ... Bulls G Jimmy Butler (right toe) is traveling with the team, but there's no timetable for his return. ... Chicago plays its first home game since Nov. 18 on Monday against New Orleans, the first of four straight games at the United Center. ... The Cavaliers don't play again until Wednesday when Denver visits.