The 'Forever' singer was rumoured to have split with Tran after being photographed sitting with ex-girlfriend Rihanna at Jay-Z's New York concert on Wednesday (October 3).
Tran seemingly reacted to the news by cryptically tweeting: "Bye baby."
Brown has now acknowledged that his romance with Tran has ended because of his renewed friendship with Rihanna.
"I have decided to be single to focus on my career. I love Karrueche very much but I don't want to see her hurt over my friendship with Rihanna," Brown said in a statement.
He continued: "I'd rather be single allowing us to both be happy in our lives."
Brown and Rihanna famously dated for several years early in their careers, but split following a domestic dispute in 2009.
Rihanna recently told Oprah Winfrey that she and Brown still "love each other" in spite of their troubled past.
Rumours of a renewed romance intensified earlier in the week when Brown and Rihanna were apparently seen "hugging and kissing" at a New York nightclub.
Watch Chris Brown's 'Forever' music video below: