Autophosphorylation of αCaMKII is regarded as a ‘molecular memory’ for Ca2+ transients and a crucial mechanism in aversely, but less so in appetitively, motivated learning and memory. While there is a growing body of research implicating αCaMKII in general in behavioral responses to threat or fearful stimuli, little is known about the contribution of the autophosphorylation. The present study asked how αCaMKII autophosphorylation controls anxiety-like behavioral responses toward novel, potentially threatening stimuli. We tested homozygous and heterozygous T286A αCaMKII autophosphorylation deficient mice and wild types in a systematic series of behavioral tests. Homozygous mutants were more active in the open field test and showed reduced anxiety-related behavior in the light/dark test, but these findings were confounded by a hyperlocomotor phenotype. The analysis of elevated plus maze showed significantly reduced anxiety-related behavior in the αCaMKII autophosphorylation-deficient mice which appeared to mediate a hyperlocomotor response. An analysis of home cage behavior, where neither novel nor threatening stimuli were present, showed no differences in locomotor activity between genotypes. Increased locomotion was not observed in the novel object exploration test in the αCaMKII autophosphorylation-deficient mice, implying that hyperactivity does not occur in response to discrete novel stimuli. The present data suggest that the behavior of αCaMKII autophosphorylation-deficient mice cannot simply be described as a low anxiety phenotype. Instead it is suggested that αCaMKII autophosphorylation influences locomotor reactivity to novel environments that are potentially, but not necessarily threatening.