Police sources told ABC News, ESPN, the New York Post and Houston Chronicle that Porter had been locked out of his hotel room and after hotel security helped him enter, he attacked his girlfriend, a former Women's NBA player.
The woman, identified as Kysre Gondrezick, was taken to a hospital with neck pain and a cut on her face, according to the reports, while Porter was taken into custody.
They had appeared together at a Fashion Week event.
Porter, 23, was a first-round pick in the 2019 NBA Draft and played one season for the Cleveland Cavaliers before being traded to the Rockets in January 2021.
"We are in the process of gathering information surrounding the matter involving Kevin Porter Jr.," the Rockets said in a statement.
An NBA spokesman told The Athletic and ESPN the league was aware of the reports and in contact with the Rockets while gathering more information.
Porter heads into the upcoming NBA campaign off the best season of his career, having averaged career-highs of 19.2 points, 5.3 rebounds and 1.4 steals a game for Houston last season as well as 5.7 assists and a career-high 44.2% shooting accuracy rate.