His character is said to have been admirable. His fearless loyalty to the truth is shown by his persistence in associating with Imam Bukhari despite the political pressures brought to bear on the latter. Like Imam Bukhari, he adhered to the usual Islamic ethic of refusing to speak ill of anyone.
Imam Muslim adhered strictly to the path of righteousness. He was in fact a great saint of a very high calibre. His excellent character can be well judged from the simple fact that he never ever indulged in backbiting, a very common human failing. He had a remarkable memory. Ishaq bin Rahwi said of Imam Muslim: "I wonder what this person is going to be?" This was said in his youth. Ishaq Kausar once addressed Imam Muslim and said: "Your presence in the muslim community will always keep it in the good." Abu Saimah who was a colleague of Imam Muslim and was so attached to him that while Imam Sahib was busy compiling the Sahih Muslim, he remained in Imam Sahib's company for fifteen years. He never told a lie nor did he ever use vulgar words.