Clinton was scheduled to campaign along with Vice President Joe Biden in Pennsylvania.
"Due to the tragic events in Dallas, the July 8 Hillary for America campaign event with Vice President Biden will be postponed," the campaign said in a statement.
Trump was scheduled to hold an election rally in Miami, Florida.
"The Trump Campaign has cancelled the trip to Miami, Florida today, due to the tragic events in Dallas last night," his campaign said in another statement.
This is for the second time that election rallies have been canceled due to tragic violent incidents in the country.
Last month, Trump and Clinton cancelled their campaign events after the horrific mass shooting at a gay club in Orlando, Florida.