Kimmel's comments come two days after the deadly shooting at a school in Florida that claimed the lives of 17.
An emotional Kimmel opened his show with a monologue by speaking to both his audience and President Trump. He pleaded with Trump to address the issue of gun violence.
"As I'm sure you know and feel, this is another very sad day in America. Another senseless shooting. This time at a high school in Parkland, Florida, where a gunman, a former student, opened fire yesterday again.
He then played excerpts from Trump's speech in the aftermath of the Florida shooting, in which he promised to act on mental health.
More From This Section
"Do something! We still haven't even talked about it. You still haven't done anything about it. You've literally done nothing. Actually, you've done worse than nothing.
"You like to say this is a mental health issue, but one of your very first acts as president, Mr Trump, was to actually roll back the regulations that were designed to keep firearms out of the hands of the mentally ill. You did that. Your party voted to repeal the mandates on coverage for mental health," Kimmel said.
"Somewhere along the line, these guys forgot they work for us, not the NRA. Us. And this time we're not going to allow you to bow your head in prayer for two weeks, until you get an all-clear and we move on to the next thing. We're going to make sure you do something this time," Kimmel said.