Maternal immune activation (MIA) can affect fetal brain development and thus behavior of young and adult offspring. Reports have shown that increased Interleukin-6 (IL-6) in the maternal serum plays a key role in altering fetal brain development, and may impair social behaviors in the offspring. Interestingly, these effects could be attenuated by blocking IL-6. The current study investigated the effects of luteolin, a citrus bioflavonoid, and its structural analog, diosmin, on IL-6 induced JAK2/STAT3 (Janus tyrosine kinase-2/signal transducer and activator of transcription-3) phosphorylation and signaling as well as behavioral phenotypes of MIA offspring. Luteolin and diosmin inhibited neuronal JAK2/STAT3 phosphorylation both in vitro and in vivo following IL-6 challenge as well as significantly diminishing behavioral deficits in social interaction. Importantly, our results showed that diosmin (10 mg/kg day) was able to block the STAT3 signal pathway; significantly opposing MIA-induced abnormal behavior and neuropathological abnormalities in MIA/adult offspring. Diosmin's molecular inhibition of JAK2/STAT3 pathway may underlie the attenuation of abnormal social interaction in IL-6/MIA adult offspring.