Activity-dependent neuroprotective protein (ADNP) is a most frequent autism spectrum disorder (ASD)-associated gene and the only protein significantly decreasing in the serum of Alzheimer's disease (AD) patients. Is ADNP associated with ASD being more prevalent in boys and AD more prevalent in women? Our results revealed sex-related learning/memory differences in mice, reflecting hippocampal expression changes in ADNP and ADNP-controlled AD/ASD risk genes. Hippocampal ADNP transcript content was doubled in male vs female mice, with females showing equal expression to ADNP haploinsufficient (ADNP(+/)(-)) males and no significant genotype-associated reduction. Increased male ADNP expression was replicated in human postmortem hippocampal samples. The hippocampal transcript for apolipoprotein E (the major risk gene for AD) was doubled in female mice compared with males, and further doubled in the ADNP(+/-) females, contrasting a decrease in ADNP(+/-) males. Previously, overexpression of the eukaryotic translation initiation factor 4E (eIF4E) led to ASD-like phenotype in mice. Here, we identified binding sites on ADNP for eIF4E and co-immunoprecipitation. Furthermore, hippocampal eIF4E expression was specifically increased in young ADNP(+/-) male mice. Behaviorally, ADNP(+/-) male mice exhibited deficiencies in object recognition and social memory compared with ADNP(+/+) mice, while ADNP(+/-) females were partially spared. Contrasting males, which preferred novel over familiar mice, ADNP(+/+) females showed no preference to novel mice and ADNP(+/-) females did not prefer mice over object. ADNP expression, positioned as a master regulator of key ASD and AD risk genes, introduces a novel concept of hippocampal gene-regulated sexual dimorphism and an ADNP(+/-) animal model for translational psychiatry.