This study is the first to identify a cerebral artery‐specific impairment of Kv7 channel function in a tauopathy‐associated dementia mouse model and we suggest this functional attenuation might be due to a downregulation of the ancillary subunit, KCNE5 in the cerebral arteries of the rTg4510 mice. Here, KCNE5 is linked to tauopathy.