The novel neuroprotective action of Humanin (HN), especially its derivative [Gly¹⁴]‐humanin (HNG), against Alzheimer's disease (AD)‐related insults has been reported. However, it is still short of electrophysiological evidence for the protection of HN on synaptic plasticity, and the molecular mechanisms that underlie the neuroprotective function of HN remain largely unknown. The present study examined the effects of intracerebroventricular (i.c.v.) injection of HNG on amyloid β (Aβ), a main constituent of senile plaques in the AD brain, induced suppression of long‐term potentiation (LTP) in the rat hippocampal CA1 region in vivo and investigated the possible mechanism of HNG in LTP protection. We found that application of Aβ fragments 25–35 (Aβ25–35) and 31–35 (Aβ31–35) significantly inhibited high frequency stimulation‐induced LTP, while HNG effectively prevented the suppression of LTP induced by Aβ fragments in a dose‐dependent manner. After pretreatment with Genistein, a tyrosine kinase inhibitor, the protective action of HNG on LTP was nearly completely abolished. Therefore, the present study demonstrated for the first time that HNG could protect against the neurotoxic Aβ‐induced hippocampal LTP impairment and the tyrosine kinase pathway was involved in the neuroprotective action of HNG, suggesting that HNG might be one of the promising candidates for the treatment of AD in the future. Synapse 64:83–91, 2010. © 2009 Wiley‐Liss, Inc.