Paul Pierce had 19 points, six rebounds and five assists and Glen Davis came off the bench to score 18 points as Boston beat Los Angeles 96-89 in game four of the NBA finals on Thursday.
Reserve guard Nate Robinson had 12 points for the Celtics who used a balanced scoring attack to beat the Lakers and level the best-of-seven championship series at two games apiece.
"It was all will and determination," said Davis. "I am proud of our guys. We played great.
"This is where you grab the moment. It is immortality. All you can do is play in the moment."
The sold out Boston Garden crowd of 18,624 was treated to a superb performance by the Celtics' bench players in what started out as a defensive battle before Boston busted loose in the fourth. Game five is Sunday in Boston.
The Celtics, who won it all in 2008, are seeking their NBA record 18th title while defending champion Los Angeles are looking for their 16th title in franchise history.
The Celtics kept it close through three quarters then got their offence untracked by outscoring the Lakers 34-29 in the fourth quarter.
"We knew we had to bring our energy," Robinson said. "We stayed together and kept our composure. I wanted to fire the crowd up."
Kobe Bryant finished with 33 points and Pau Gasol had 21 points for the Lakers.
Boston's Paul Pierce buried an NBA finals record eight threes in game two but Thursday it was Bryant's turn.
Bryant nailed six-of-11 from the arc but he also finished the game with five fouls and committed seven turnovers as the Celtics did a good job of making sure one of the best closers in the NBA didn't take over the game in the final two minutes.
The Celtics came out with another great start for the second game in a row and led 19-16 at the end of the first before allowing the Lakers to take a 45-42 lead at the half time largely dur to shoddy defense.
Coach Jackson admits Bryant fatigued
Kobe Bryant called his seven-turnover performance in Thursday's 96-89 NBA finals loss to the Boston Celtics "horrible" as Los Angeles Lakers coach Phil Jackson put it down to exhaustion.
"He was tired," Jackson told reporters after the Celtics evened the best-of-seven series at two games apiece on their home court.
"Physically he had to work too hard in the course of the game and couldn't finish it out the way he wanted to which is a shame.
"The match-ups in the game kind of dictated those terms and we'll have to do something different the next game to get him off the floor and keep him ready for that fourth quarter."