De Niro pleaded his case in an open letter titled, 'Robert Mueller, We Need to Hear More', published by the New York Times.
The actor, who has portrayed Mueller on "Saturday Night Live", has argued that the Special Counsel's 400-page report does not speak for itself as Mueller has said it does, because it is not written plainly enough for the average American to understand, reported dailymail.co.uk.
"Your life has been a shining example of bravely and selflessly doing things for the good of our country. I urge you to leave your comfort zone and do that again," De Niro wrote, addressing Mueller.
"It (your report) may speak for itself to lawyers and lawmakers who have the patience and obligation to read through the more than 400 pages of carefully chosen words and nuanced conclusions (with all due respect, as good a read as it is, you're no Stephen King)," he added.
He further said that President Donald Trump's statements are so loud and persistent that they need to be refuted.
After his redacted report was released last month, Mueller held a press conference on Wednesday where he stated that he did not clear Trump of wrongdoing, but that his office would not offer additional commentary on the subject, while announcing his resignation from the Federal Bureau of Investigation.
During the conference, Mueller asked Americans to read his full report, saying "it speaks for itself" and requires no additional comment from him.
Throughout the course of Mueller's two-year investigation into the alleged Russian interference in the 2016 presidential election, he and his office endured a barrage of attacks from Trump, who repeatedly called the probe a "witch hunt".
De Niro, in his letter to Mueller, further said: "While I and so many Americans have admired your quiet, confident, dignified response in ignoring that assault, it allowed the administration to use its own voice to control the narrative.
"And those voices are so loud and so persistent that they beat even reasonable people into submission. The loudest, most persistent voice belongs to the president himself, and under most circumstances, we want to believe our president."
( With inputs from IANS )