Prior to her short-lived stint at MSNBC, Van Susteren hosted a program on Fox News for 14 years where she interviewed then-candidate Trump.
And the president said on Saturday that it was because she wouldn't go along with the network's theme of nonstop bashing of him.
Trump's accusation on Saturday that she declined to comply with MSNBC's alleged trend of "Trump hate" was the second time in recent days that the president attacked the network.
With the Fox and MSNBC audiences usually diametrically opposed, it proved a poor fit.
"MSNBC and Greta Van Susteren have chosen to part ways", said Griffin, in the memo. It was the least-watched show on MSNBC between 5 p.m. and midnight both Monday and Tuesday of this week, according to the Nielsen company. She had no immediate comment about the ouster.
The president first weighed in on former MSNBC host Greta Van Susteren's departure from the network, writing that she was "let go by her out of control bosses at NBC [and] Comcast because she refused to go along [with] 'Trump hate!'" "We are grateful to her and wish her the best".
A lawyer like Van Susteren, Melber is MSNBC's chief legal correspondent and hosts a weekend show, "The Point".
While one can make the case that Van Susteren wasn't as anti-Trump as numerous other hosts in the MSNBC lineup, she did speak critically of the president's actions from time to time. He'll begin as permanent 6 p.m. host sometime next month, Griffin said.