Personality and dogmatic thinking within religious individuals have been examined by previous research, but neglected for non-religious individuals. In this experiment, we distinguish between two types of non-religious groups; those who ascribe themselves to an identity (atheists) and those who do not (no beliefs in particular). A total of 103 nonreligious individuals (36% atheists and 64% with no particular beliefs) completed an online questionnaire measuring dogmatism and openness traits, with an additional Christian group (n = 91) serving as a control. After confirming a relationship between identity salience and dogmatism, and validating a measure of dogmatism (DOG) in both non-religious groups, we note key personality differences between the two. Those with no beliefs in particular demonstrated a traditional negative correlation between openness and dogmatism (along with Christians) while these variables correlated positively for atheists (in particular, on 'unconventionality'). This study is the first to establish differences between the relationship of dogmatism and openness within non-religious populations and explain these differences through group identity. Thus, identity strength and group belief systems are suggested to be key contributors to observed group differences between non-religious individuals.