"We actually think the impact on of an Amazon smartphone on the iPhone would be the same impact say that a Kindle Tablet Fire HD on the iPad, i.e., not that much," he Tuesday on CNBC's "Fast Money."
Amazon has continued to encroach on Apple's territory recently with a push into streaming video and content, as well as just announcing a new music streaming service.
"There's probably not a large chance of this actually taking away from the iOS sub base—the installed base—I think it's much more likely it would be taking away from other Android franchises," he added.
Marshall has a "buy" rating on Apple with a $96 price target.
—By CNBC's Kristin Cwalinski