The trait-state isomorphism hypothesis holds that personality traits and states (i.e., trait-related behaviour) are characterized by similar outcomes (Fleeson, 2001). For example, both trait and state extraversion are associated with positive affect, and negative affect is associated with both trait and state neuroticism. However, research has not yet investigated whether the traits and states of ‘openness to experience’ are isomorphic. Openness reflects a general tendency to engage with abstract and sensory information and is associated with creative thinking, personal growth, and to a lesser extent, positive affect. In the present experiment, participants (N = 210) completed a pretest assessment, five daily exercises designed to either be inert (control condition) or engage the behaviours and cognitions associated with openness (experimental condition), a post-test assessment, and a two week follow up assessment. Results supported the isomorphism hypothesis for positive affect but not creative thinking ability or personal growth.