In this play, which begins with masking and disguising of one's feelings, the audience will hardly be surprised that one more disguise should appear at the end. In this case Hero is wearing a veil to hide her face so that she can pretend to be her "fictional" cousin and marry Claudio under that disguise.
Leonato and the others now have fully investigated Don John's scheme and know all of the details about that matter; but as to that other scheme regarding the bringing together of Beatrice and Benedick, Leonato still does not understand everything. When Benedick admits that he loves Beatrice, Leonato exclaims the following:
The sight whereof I think you had from me, From Claudio, and the Prince. (25-26)
Leonato still believes that Benedick's love is completely a result of Don Pedro's scheme. He never does realize that Benedick had always had feelings for Beatrice. However, that does not matter. The audience knows. Benedick then asks Leonato for his help because Benedick wishes to marry Beatrice. Thus, the play ends with two weddings.
Claudio, still believing that Hero is her own cousin, agrees to marry her before he is able to see her face. After Claudio gives his solemn vow to be her husband, Hero removes the veil (line 60).
Claudio is amazed when he sees Hero, but the Friar who performs the wedding explains everything to him (lines 67-71).
Of course, the really central figures of the play are Beatrice and Benedick. Both of them are afraid of revealing their feelings first. Both are afraid that the other might change his or her mind.
BEATRICE Do not you love me?
BENEDICK Troth no, no more than reason. (77)
As Shakespeare always admits, love is an emotion that has nothing to do with reason. Thus, Benedick declares that he does not love Beatrice any more than reason allows (which is none). Still, this line might also be interpreted to mean that Benedick loves Beatrice in an amount that goes beyond reason. The line could mean that Benedick loves Beatrice even though love is not reasonable.
Beatrice also declares (in a similar manner that could also be interpreted in different ways) that she does not love Benedick (line 83). For a moment the audience may fear that Benedick and Beatrice's pride and stubbornness will prevent them from getting married. But then Claudio pulls out a love poem that Benedick had written to Beatrice, and Hero pulls out a love letter that Beatrice had written to Benedick. Their own writing contradicts their statements. Their own writing shows that they do love each other, and so they get married.
The play ends with a messenger bringing news that Don John had been captured, but Benedick declares that his punishment can wait for another day. So, instead, the play ends with a festive song and dance. The plays ends with celebration and carnival.