Deslauriers, ostensibly Frédéric’s best and oldest friend, is deeply admiring of Frédéric as well as bitterly jealous. He and Frédéric take turns disappointing each other. At times, Deslauriers seems to play a spouselike role in Frédéric’s life. When they were young, they excitedly planned out their future, imagining themselves traveling, working, and living together. Deslauriers is the first to taint the dream, when he forgoes Paris to take a job in Troyes. At this point in their friendship, Deslauriers is so influential in Frédéric’s life that Frédéric wonders how he can possibly stay in Paris without him and feels shaken by the amount of confidence he has in his friend. Deslauriers has put his own interests first, and this seems like a significant betrayal.
When Frédéric begins flirting with high society and pursuing various women, it is Deslauriers who finds himself overlooked and left behind. When he returns to Paris, Frédéric brushes him off; Deslauriers, with his shabby appearance, embarrasses Frédéric, who has come into money and now spends lavishly on his clothes and accoutrements. Deslauriers envies him, and this envy quickly turns ugly. He tries to steal Madame Arnoux from Frédéric (to the extent that she can be stolen); he attempts to win over Rosanette, and may eventually succeed; and he considers offering himself for a job for which Frédéric has been tapped. These are actual betrayals on both friends’ parts. Only when Deslauriers eventually achieves his own success and Frédéric has been chastened for his extravagance can the two rebuild a genuine friendship.