Back in Whoville, Cindy Lou Who asks her family about The Grinch. They warn her about the not-very-nice creature (“He Hates Christmas Eve”). The Grinch imagines what Christmas morning will be like, as he is filled with nightmarish visions of opening presents and feasting. He complains that Christmas is annoying, loud, and inauthentic (“Watchamawho”). Meanwhile, the Whos continue to sing carols about gifts and giving (“Fah Who Foraze”). Finally, the Grinch has a big idea: he will stop Christmas himself (“I hate Christmas Eve Reprise”)!

Back in Whoville, the Whos are shopping for their final gifts. They hustle and bustle happily in and out of shops through the snow (“Last Minute Shopping”). Cindy Lou spots The Grinch right there in the middle of Whoville. The Whos tentatively introduce themselves to him and even invite him to join them for Christmas in the morning. The Grinch appears overly enthusiastic to the discomfort of all. The Grinch asks what Cindy Lou would like as a gift, she says she is hoping for a red rocking horse. The Grinch menacingly wishes her the best, then takes his leave to do his own shopping. He buys a red jacket, bunting, elastic, and wool and returns to his cave (“You’re a Mean One/The Grinch Goes Shopping”).

Once there, The Grinch crafts himself a Santa Claus costume and puts reindeer antlers on Max. The Grinch proclaims that he is the only one of his kind, and he claims to be happy as a friendless loner (“I’m One of a Kind”).

Down at the bottom of the mountain, Grandma, Grandpa, and Mama Who are placing gifts around the tree. Grandpa Who, hard of hearing, keeps mishearing what the others say. The Whos sing about all the preparation for Christmas, and about how happy the children will be (“Now’s the Time”).

The Grinch and Max are atop the Who house, banging and clanging. Suddenly, Max falls from the chimney into the fireplace, quickly followed by The Grinch. Max begs him not to take the Whos’ food, but The Grinch gleefully replies that he will take it all. He begins to stuff all the gifts, decorations, and food into his bags (“Never Never Very Merry Christmas”). As he is dragging the tree to the fireplace, Cindy Lou appears, mistaking The Grinch for Santa Claus, and asks why he is taking the tree. The Grinch thinks quickly and lies, saying he is taking it back to his workshop to fix the lights. Cindy Lou thinks this is a fine answer and simply requests he have it back for the morning.

Trying to get her to go away, The Grinch asks why she is not in bed. Cindy Lou begins to cry and throws herself on The Grinch for a hug explaining that she had a bad dream. Cindy Lou asks him if he will spend Christmas with his family, the Grinch says that no, Santa always spends Christmas alone. Cindy Lou is shocked by this (“Santa For a Day”) Something begins to change inside The Grinch, he fixes the light on the tree and returns it to its spot in the room. As Cindy Lou begins to return to bed, The Grinch tenderly asks her what her nightmare was about. She, feeling emboldened, proclaims it was about “that nasty old Grinch!” The Grinch immediately toughens and after Cindy Lou has left, tears the lights off of the tree (“You’re a Mean One Reprise”).

The next morning, as the Whos wake up on Christmas, they explore their empty home and Cindy Lou explains that it was a “sort of a Santy Claus.” Then she tells her family that he was very lonely with no family, no friends, and no gifts.

On the top of Mt. Crumpit, The Grinch is excited to hear the unhappy Whos as they wake up to their ruined Christmas. But as they sit and listen, the Whos begin singing (“Welcome Christmas Reprise”). The Grinch wonders if Christmas, “doesn’t come from a store. Maybe Christmas…perhaps…Means a little bit more?” Max comforts The Grinch by explaining that he is special (“I’m One of a Kind Reprise”). The Grinch begins to think that perhaps by being alone, he is missing out and that he might be beginning to like the Whos—so much, in fact, that it hurts. And just then, his heart grows three sizes!

The sleigh, teetering on the edge of the mountain, begins to slip over the edge just as Max and The Grinch jump in. Old Max, as the narrator, returns to the mouth of the cave, packs up his suitcase, and leaves. The Grinch arrives in his sleigh, and the Whos stand back, unsure. The Grinch, after several attempts, succeeds in wishing the Whos a Merry Christmas. All applaud and cheer. As he hands Cindy Lou a red rocking horse, she tells him that although the gifts are nice, he was the most important thing missing from Christmas (“Finale”).