Some protesters carried "I Can't Breathe" signs in reference to the death of Eric Garner, a black man who died after a white police officer restrained him in a choke hold. Protesters took to the street last week after a grand jury chose not to indict the officer.
"Today, the protesters decided to come here, to the Barclays Center," CBC's Steven D'Souza reported from the scene of the demonstration. "What they are yelling to the police and to the world is 'You serve us,' one of the many chants that we're hearing from the protesters."
"There is a feeling here that having this protest now, with the royals in the building, will give it worldwide attention," D'Souza said of the protest in Brooklyn. The protests, which spotlight not only Garner's case but that of slain Missouri teenager Michael Brown and others affected by police violence, has been relatively peaceful so far, D'Souza said.
At the game, Cleveland's star player, LeBron James, sported a shirt that said "I Can't Breathe" during the warm-up.
As the royal couple headed to their seats during the third quarter, fans stood and cheered. The royals were shown on the overhead scoreboard during a stoppage of play. Kate, wearing a grey jacket, waved to the camera as the crowd roared. Jay-Z and Beyonce were led across the court between the third and fourth quarters to chat with them.
Tonight's NBA game is just one stop on a busy agenda that took the Duke of Cambridge to Washington earlier in the day to speak about preventing illegal wildlife trafficking. The duchess stayed in New York City for her events, which included a visit to a centre for at-risk children.