Aim: BACE1 is the secretase that acts in Aβ production in Alzheimer's disease (AD). Materials & methods: We investigated mRNA expression in total blood and the levels of plasma protein BACE1 in AD patients compared with cognitively healthy subjects. Probable AD (n = 47) and non-AD control group (n = 32) were evaluated for mRNA expression for BACE1 using reverse transcription-qPCR. A subsample of n = 21 AD and n = 20 non-AD had plasma BACE1 levels analyzed, using ELISA. Results: No differences were found on BACE1 mRNA between groups. However, higher levels of BACE1 were detected in plasma of AD patients. Discussion: Blood-based diagnostic tools are desired to improve AD diagnosis. BACE1 plasma levels could provide an additional diagnostic tool for AD in association with neuropsychological tests.