Shapiro had been scheduled to appear Wednesday night at the Ronald Reagan Presidential Library to discuss his new book.
The announcement of the cancellation was made after Kirk was shot but before President Donald Trump confirmed Kirk's death in a social media post.
Kirk, who rose from a teenage conservative campus activist to a top podcaster, culture warrior and Trump ally, was shot and killed Wednesday during one of his trademark public appearances at a college in Utah. He was 31.
Kirk died doing what made him a potent political force - rallying the right on a college campus, this time Utah Valley University. His shooting was one of an escalating number of attacks on political figures, from the assassination of a Democratic state lawmaker and her husband in Minnesota to last summer's shooting of Trump, that have roiled the nation.
Whether Shapiro's event at the Reagan library would be rescheduled was unclear.
Charlie Kirk shot during event at Utah university
The Associated Press and City News Service contributed to this report.