"THERE IS NO TRADE dont know where this info came from!" the 35-year-old right-hander posted on his official Twitter account Monday as the Cubs were in Pittsburgh to play the Pirates.
The denial came after MLB.com reported the package deal may include 22-year-old Atlanta right-hander Randall Delgado, who is 4-9 with a 4.22 earned-run average.
CBSSports.com and ESPN.com were among other outlets reporting the trade was in the works Monday, though the Cubs would not confirm it had been completed and said no announcement was scheduled.
Dempster, 35, who is 5-4 with a 2.11 ERA, confirmed weeks ago he was willing to waive his 5-and-10 rights to allow a trade to a contender.
Atlanta is tied with Washington for first place in the National League East while the Cubs are mired in fifth place in the NL Central, 13 1/2 games behind division-leading Pittsburgh and Cincinnati.