Entertainment Weekly claims that the former House star is in line to play a major new love interest for Ted (Josh Radnor).
The character, who could appear in up to 13 episodes, is described as "a quick-witted, rabble-rousing activist" who clashes with Ted over the planned demolition of a historic New York hotel.
However, Morrison is said to be facing competition for the role from both former Friday Night Lights star Minka Kelly and Jacinda Barrett.
It was previously announced that the actress would make a guest appearance on forthcoming NBC drama Chase.
How I Met Your Mother returns to CBS on September 20.