Everitt Jameson pleaded guilty to attempting to provide material support and resources to ISIS.
MORE: California man planned ISIS-inspired Christmas terror attack on San Francisco's Pier 39, FBI says
Jameson was arrested last December after telling undercover FBI agents, one of whom he thought worked for ISIS, of plans to use pipe bombs and guns to kill tourists at Pier 39.
A federal magistrate earlier found that Jameson appears to have a mental health condition.