In the Western countries, about half of the non-believers/non-religious self-identify as agnostic, not as atheist. Does this convictional status reflect only epistemic differences between these two types of non-believers (“I do not know” vs. “God does not exist”) or also deeper personality and other individual differences? We theorized that agnostics, compared to religionists and atheists, should be (1) the highest in (1a) neuroticism and related-traits (indecisiveness, attachment insecurity), as well as (1b) open-mindedness-like characteristics. They should also be (2) midway between religionists (high end) and atheists (low end) on (2a) prosocial dispositions and (2b) spirituality, especially immanent forms of it, and related to it cognitive style and beliefs (intuitive thinking, paranormal beliefs). Finally, agnostics should be higher in humility compared to atheists. We investigated the above questions through three studies in secularized European contexts providing meaningful, mostly replicable, and nuanced results.