Outgoing Secretary of State Rex Tillerson called Washington, DC, "a very mean-spirited town" in his farewell address to State Department employees on Thursday.

Tillerson received a warm reception from his colleagues, who gave him a standing ovation at the end of his speech.

President Donald Trump fired Tillerson on March 13, and he'll officially end his tenure at the end of the month.

Outgoing Secretary of State Rex Tillerson gave a farewell speech on Thursday in a speech that drew a standing ovation and applause from employees at the State Department.

Tillerson urged his colleagues to never lose sight of their integrity, even amid the tumult of Washington politics.

"This can be a very mean-spirited town," Tillerson said. "But you don't have to choose to participate in that. Each of us gets to choose the person we want to be, and the way we want to be treated, and the way we will treat others."

He continued: "In these times, your continued diligence and devotion to the State Department's mission has never been more necessary. As you go about your duties, each of you carrying out your individual responsibilities as well as your collective duty, it is my hope that you will be guided by and test your actions each day against the values that we have spoken about this past year."

President Donald Trump parted ways with Tillerson on March 13, citing policy disagreements as the reason for his firing. Tillerson found out via tweet.

"We got along actually quite well, but we disagreed on things," Trump said. "When you look at the Iran deal, I thought it was terrible. He thought it was okay. I wanted to either break it or do something; he felt a little differently."

President Donald Trump and Secretary of State Rex Tillerson during a bilateral meeting. AP Photo/Alex Brandon

Tillerson will officially leave his post at the end of the month. Trump nominated CIA Director Mike Pompeo to replace him.

Tillerson's departure marks the end of his up-and-down tenure at the State Department, where he served for just 14 months. The former CEO of ExxonMobil occasionally contradicted Trump on policy, including Iran and North Korea.

Last August, when Trump warned North Korea that it would "be met with fire and fury like the world has never seen" if it continued to threaten the US, Tillerson took a much more diplomatic approach.

"What the president was doing was sending a strong message to North Korea in a language that Kim Jong Un would understand ... Americans should sleep well at night," Tillerson said.

Then in October, NBC News reported that Tillerson called Trump a "moron" over a politicized speech the president delivered to a gathering of the Boy Scouts of America. Tillerson never denied the report.