You can watch the full series of The Mentalist streaming on Hulu. It is also available for purchase or rent on Amazon Video, Apple TV, and Fandango At Home. Additionally, The Mentalist can be streamed on NOW TV (available in some regions) with all 7 seasons accessible. There are no free streaming options currently for The Mentalist on major platforms, but Hulu is the primary subscription streaming service offering it. For purchase options, you can check platforms like Amazon and Apple TV as well.