Subcritical water (SCW) extract of blue mussel was prepared at 100, 200, and 300 °C for 10, 30, and 60 min, respectively, and its effect on the activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, angiotensin-converting enzyme (ACE), and acetylcholinesterase (AChE) was evaluated. We found that DPPH radical scavenging, ACE inhibitory, and AChE inhibitory activities significantly increased with increasing extraction temperature and duration. For example, AChE inhibitory activity of the extract at 300 °C for 60 min increased to 63.1 ± 0.3%, while that at 100 °C for 10 min was 5.6 ± 0.3%. The results suggested that SCW extraction is attractive processing methods for obtaining high valued extract from blue mussel.