In a play that concerns itself so much with the sexual mores of its day and deception and trickery, Mirabell is clearly the protagonist in this play who uses his charms and beauty to gain what he wants. He is the suitor of Millamant and has something of an "interesting" history, as he used to be the former paramour of Mrs. Fainall, and also deliberately flirts with mrs. Marwood. He has also managed to turn Lady Wishfort against him through deliberately pretending to be in love with her. Mirabell shows himself to be a very intelligent and canny strategist, as he develops and enacts stratagems that will enable him to marry Millamant, Lady Wishfort's niece, against Lady Wishfort's will and also gain Millamant's rather impressive dowry.
He is a character that seems to divide audiences. On the one hand, he possesses a certain irrascible charm and charismatic nature that makes him attractive, however, it is clear that he heartlessly exploits those around him to gain success in his endeavours. What is his saving grace is the way in which all seem to benefit from his stratagems, so that nobody seems to mind. The only people who definitely do take issue with him is Fainall and Marwood, because he shows them up to be the traitors that they really are. Perhaps we sympathise with him because he is a raconteur who is nevertheless hopelessly in love, and is determined to use all of his wits to satisfy his passions.
What is interesting about his character is that Congreve, rather ironically perhaps, chooses to give him the final moral at the closing of the play:
From hence let those be warned, who mean to wed,
Lest mutual falsehood stain the bridal-bed:
For each deceiver to his cost may find
That marriage frauds too oft are paid in kind.
The irony is evident: Mirabell, a character who has been characterised by sexual infidelity, now at the close of the play, preaches against dishonesty and adultery. Perhaps we are to assume that he has changed as a result of marrying his love, or perhaps Congreve is presenting a sexual moral lesson whilst at the same time undermining its impact by allowing Mirabell, a character who has allowed deception and infidelity to govern his life, to deliver it.