The team also released a video via social media at tipoff, promoting unity.
In addition, the Rockets and New York Knicks all locked arms at midcourt during the national anthem before Tuesday's game at the Toyota Center in Houston, while the Los Angeles Lakers and Sacramento Kings joined arms during the anthem before their game, as well.
Celtics coach Brad Stevens and Jae Crowder said earlier Tuesday that the team had put a lot of time into thinking about the best way to promote positive change.
"We've had a lot of sit-down discussions about it. We've had a lot of individual discussions," Stevens said. "We've had three or four meetings after practices, sometimes just players, sometimes just us, sometimes people we've invited in from the outside to spend time with our guys. Our guys have been incredibly thoughtful, and I think, like from what I've seen across the NBA early on, I think our guys are really focused on promoting positive unity, togetherness, progress and all those types of things. But those have been, as far as deep, certainly good discussions, they've been great. And I commend our guys for sharing and for thinking and for really looking at this in a really insightful way.
"I think one of the great things about being a part of a team is you all come from different backgrounds and you learn about each other and you all come together for the common cause, and that's why we all love sports, right? We can all rally around that common cause and we can rally around teams. But I think when you really get into deep, impactful stuff, those are special conversations, and sometimes those are uncomfortable, and sometimes there can be tension around those; but I think that's the beautiful part about our group, is that they all appreciate one another, really support one another. And again, I think you'll see, like I think they're very much into what the teams that I've seen thus far, in talking about togetherness and continued progress."
Crowder said the team thought it was important to find the proper way to deliver its message.
"What do we want to portray? What do we want our message to be? That's what we had talked about -- and how can we go about doing it in a positive way? That's all we talked about," Crowder said. "We just want to make sure everybody's on the same page and everybody [can] speak on their belief. We don't want anybody to feel like they're doing something they don't want to do or talk about something they don't want to talk about. So we just wanted to make sure everybody's on the same page in those conversations that we had."
And what was the message the Celtics wanted to deliver?
"That we need change in this world," Crowder said. "We need to do it together. Just not one individual; it's got to be a team-type deal, a unity, a togetherness. Whatever we decide our message to be, it has to be about being together as one and coming together as one."
The Celtics' inspiration for the interlocked arms came from a picture of the 1960-61 Boston team, which interlocked arms in a team photo with the goal of promoting civil rights. Team officials produced the picture for the players, who quickly warmed to the idea of carrying on the legacy of those who wore the Celtics jersey before them.
Tom "Satch" Sanders, a rookie on that 1960-61 squad, spoke to the Celtics on Monday after the final practice before their preseason opener.
"What we were saying in our meetings, that we've got to do it together as a team, and that picture showed a great example of that. That's why we [said] OK, we can tie it in with us," Crowder said. "Those guys did it during a time where it was tough. It's not that bad now, but still, they did it together, they tried to make a change together, and that's where we got the idea."
Tuesday's demonstration was the first one on the court for the Rockets. When they played their first preseason game Sunday against the Shanghai Sharks, the entire team stood at attention for the playing of the American and Chinese anthems.
"They were on board with it, and it was just a matter of us coming together and showing everybody we're united," Anthony said.
Said Noah: "I think it was very respectful, but at the same time [it brought] awareness to some of those issues."
Harden said the demonstration represented "a brotherhood" and that the message was unity.
"Just standing together for something that we believe in; obviously we know what's going on around the world," he said. "We wanted to use our high power and noticeability to just go out there and make it aware that we're going to stand together, not just the two teams, but the entire league.
"We want to use our platform to show people that we're together and we're behind them in this. ... It's something that we'll continue to do, and we have a platform and we want to use it. It's just the beginning."
The Los Angeles Lakers released a statement supporting their players.
"We fully support our players in exercising their right of expression over an issue that is so important," the statement read. "We also applaud the NBA and the NBA Players Association for their collaborative work in expanding the dialogue and for their spirit of cooperation."
Many players across multiple sports, led by San Francisco 49ers quarterback Colin Kaepernick, have taken a knee, locked arms or raised fists during the national anthem in protest of police brutality against African-Americans and other societal issues.
ESPN's Calvin Watkins, Ian Begley and Baxter Holmes contributed to this report.