Doherty, 27, and his band, Babyshambles, were on a flight to Barcelona from Gatwick airport, easyJet spokeswoman Samantha Day said in London. The captain radioed ahead to ask police to meet the plane at El Prat airport after noticing suspicious behavior by Doherty, she said.
"The captain asked for a police presence because a passenger was taking too much time in the bathroom and he suspected that he might be taking drugs," Javier Gaspar, a civil guard spokesman in Barcelona, told The Associated Press.
The airline said a syringe had been found in the bathroom, but Gaspar said: "We have found no syringe, nor any illegal substances."
Doherty was apparently traveling to the Primavera Sound Festival. He was released without charge but Doherty and his band have been banned from flying on easyJet, Day said.
The troubled British rocker has a history of arrests for alleged drug use. He gained international attention last year after a London newspaper published pictures of then-girlfriend Kate Moss allegedly taking cocaine at a music studio where Doherty and Babyshambles were recording.