The network's broadcast of events including gymnastics and swimming took in an average of 31.43 million viewers between 8-11pm.
It also scored an 18-49 demo rating of 10.5, which is 0.2 higher than the equivalent day in 2008's coverage from Beijing.
ABC's Bachelor Pad was clearly affected by the Olympics, as it fell 27% from last week's season premiere to 1.1 (3.48m) at 8-10pm.
Glass House also fell 25% to a series low of 0.6 (1.67m) at 10pm.
Fox, The CW and CBS aired only repeats for the whole evening, with the highest rating going to Fox's Hell's Kitchen with 1.2 (2.86m) at 9pm.
Photo gallery - London 2012 Olympics in pictures:
Copyright: Martin Rickett/PA Wire/Press Association Images