Slive and ESPN President John Skipper were to appear together in Atlanta to announce what was expected to be a new, SEC-branded college sports television network.
But in a joint statement, the pair said they had postponed the event after a pair of explosions ripped through a crowd of spectators at the marathon, killing at least three people.
"In light of the tragedy in Boston today, we have decided to postpone Tuesday's SEC/ESPN press conference in Atlanta," they said. "Our thoughts and prayers go out to all of those affected by these horrible events."
The Boston Globe reported 107 people had been injured, many of them severely, in the afternoon explosions at a busy intersection where thousands of people were lined up to watch the 117th Boston Marathon.