The advocacy group said "dozens" of activists boarded the ship as it prepared to leave for the arctic waters of Alaska.
"They're there to try to stop destructive oil drilling in the melting arctic waters, which Shell wants to start this summer," Greenpeace said in a statement.
The U.S. Interior Department's Bureau of Safety and Environmental Enforcement had approved Shell's 450-page oil-spill response plan for work in the arctic. In March, the government called on industry leaders to indicate their level of interest in oil and natural gas exploration off the southern coast of Alaska.
The Interior Department said a proposed lease in the area would cover a region with more than 75 percent of the estimated undiscovered and recoverable oil and gas resources on the Outer Continental Shelf.
Seven Greenpeace activists, including actor Lucy Lawless, were removed from the Noble Discoverer drill ship in February and arrested by New Zealand authorities. The drill ship was to leave for the Chukchi Sea off the Alaskan coast to drill exploratory oil wells.
Greenpeace said more than 380,000 supporters sent letters to Shell to protest its drilling plans for the arctic waters off Alaska's coast.