The decay rate of Be-7 electron capture was measured in C-60 and Be metal with a reference method. The half-life of Be-7 endohedral C-60 (Be-7@C-60) and Be-7 in Be metal (Be metal (Be-7)) is found to be 52.68+/-0.05 and 53.12+/-0.05 days, respectively. This amounts to a 0.83% difference in electron-capture decay half-life between Be-7@C-60 and Be metal (Be-7). Our result is a reflection of the different electron wave functions for Be-7@C-60 inside C-60 compared to the situation when Be-7 is in a Be metal.