The 20-year-old singer told his Twitter follower that he and Hailey, 18, were not dating despite hanging out together.
"People are crazy. I'm super single and this is my good friend u would know otherwise," Bieber wrote on a black-and-white picture of himself with Baldwin in a car.
"Hope that clarifies everything for everyone :) rumors are silly!," Hailey tweeted.
The two friends were spotted celebrating Hailey's birthday in New York together with Kendall and Kylie Jenner on November 19. They were again spotted in Los Angeles on December 13 and 14, sparking rumours of a romance.