WASHINGTON—Amazon.com Inc. won dismissal on Friday of an antitrust lawsuit brought against it by the District of Columbia, which had alleged that the company harmed consumers by blocking sellers on its marketplace from offering better deals elsewhere.

The lawsuit was tossed out by D.C. Superior Court Judge Hiram Puig-Lugo, according to a docket entry, based on Amazon’s motion to dismiss. The motion was opposed by D.C. Attorney General Karl Racine, whose office said it was considering an appeal.