- Act 1
- "Oh, the Thinks You Can Think!" - Cat, Jojo, Horton, Mr. Mayor, Mrs. Mayor, Gertrude, Mayzie, Sour Kangaroo, The Wickershams, and Company
- "Horton Hears a Who" - Horton, Bird Girls, Cat, Jojo, Mr. Mayor, and Jungle Citizens
- "Biggest Blame Fool" - Sour Kangaroo, Young Kangaroo, Horton, Wickersham Brothers, Bird Girls, The Cat, Gertrude, Mayzie, Jungle Citizens
- "Biggest Blame Playoff/Gertrude McFuzz" - Gertrude, Wickersham Brothers, Sour Kangaroo, The Cat, Mr. Mayor, and Jungle Citizens
- "Here on Who" - Mr. Mayor, Mrs. Mayor, Jojo, Horton, and The Whos
- "Meet Jojo the Who" - Mr. Mayor and Mrs. Mayor
- "How to Raise a Child" - Mr. Mayor and Mrs. Mayor
- "Oh, The Thinks You Can Think! (Reprise)" - The Cat and Jojo
- "It's Possible (Pt. 1)" - Jojo, The Cat, and Fish
- "it's Possible (Pt. 2)" - Jojo, The Cat, and Fish
- "Alone in the Universe" - Horton and Jojo
- "The One Feather Tail of Miss Gertrude McFuzz/Amayzing Mayzie" - Gertrude, Mayzie, and Bird Girls
- "Amayzing Gertrude (Pt. 1)" - Gertrude
- "Amayzing Gertrude (Pt. 2)" - Gertrude, The Cat, and Bird Girls
- "Monkey Around/Chasing the Whos" - The Wickershams, Sour Kangaroo, The Cat, Horton, Bird Girls, Jungle Citizens, and Whos
- "Notice Me, Horton" - Gertrude and Horton
- "How Lucky You Are" - Mayzie and The Cat
- "Mayzie's Exit/Horton Sits on the Egg/Dilemma/Hunters" - Horton, Gertrude, and Bird Girls
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- Act 2
- "Egg, Nest, and Tree" - Sour Kangaroo, Horton, Hunters, Bird Girls, and Jungle Citizens
- "Sold/Mayzie in Palm Beach" - Sour Kangaroo, Horton, Bird Girls, Jungle Citizens, Mayzie, and The Cat
- "Mayzie at the Circus" - Mayzie
- "Amayzing Horton" - Mayzie and Horton
- "Alone in the Universe (Reprise 1)" - Horton
- "Solla Sollew" - Horton, Mr. Mayor, Mrs. Mayor, Jojo, and Circus Animals
- "Gertrude/Espionage (Pt. 1)" - Gertrude
- "Gertrude/Espionage (Pt. 2)" - Gertrude and Horton
- "All for You" - Gertrude, Bird Girls, and The Cat
- "The Whos Return/The People Versus Horton the Elephant (Pt. 1)" - Horton, Mr. Mayor, Mrs. Mayor, Jojo, Gertrude, Sour Kangaroo, The Wickershams, The Cat, Yertle the Turtle, Bird Girls, and Courtroom
- "The People Versus Horton the Elephant (Pt. 2)" - Horton, Yertle the Turtle, The Cat, The Wickershams, Bird Girls, Sour Kangaroo, Mr. Mayor, Mrs. Mayor, Jojo, The Whos, and Courtroom
- "YOPP!" - Sour Kangaroo, Young Kangaroo, The Cat, Mr. Mayor, and Mrs. Mayor
- "Alone in the Universe (Reprise 2) - Horton, Gertrude, The Cat, and Jojo
- "Oh, the Thinks You Can Think! (Finale)" - Jojo and Full Company
- "Green Eggs and Ham (Finale Bows)" - Full Company
- "Exit Music" - Orchestra Members
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