That marks a 16.8 percent increase from a year ago, and makes Monday the largest online shopping day in U.S. history.
Mobile also had a record day, Adobe found, saying smartphones have become the "de facto device" for on-the-go shopping. Mobile sales on Cyber Monday reached $2 billion for the first time.
"This year, mobile shopping was dominant both in the morning and afternoon, and desktop only staged a comeback in the evening when people were home," Taylor Schreiner, director of Adobe's Digital Insights division, said.
Adobe measures 80 percent of online transactions from 100 major U.S. retailers.
Read more: Cyber Monday was largest online shopping day in US history