Don Cheadle as James "Rhodey" Rhodes / Iron Man: The co-benefactor of the Avengers, former co-CEO of Stark Industries, former officer in the U.S. Air Force, and Potts' fiancée and future husband. Cheadle reprises his role as 2012-James "Rhodey" Rhodes / Iron Man from What If… James Rhodes and Pepper Potts Were Avengers?.
Beth Hoyt as Pepper Potts / Iron Woman: The co-benefactor of the Avengers, former co-CEO of Stark Industries, the former assistant of Tony Stark, and Rhodes' fiancée and future wife. Hoyt reprises her role as 2012-Pepper Potts / Iron Woman from What If… James Rhodes and Pepper Potts Were Avengers?.
Josh Keaton as Steve Rogers / Captain America: The leader of the Avengers, World War II veteran and former fugitive, he was enhanced to the peak of human physicality by an experimental serum and frozen in suspended animation before waking up in the modern world. Keaton reprises his role as 2012-Steve Rogers / Captain America, from What If… James Rhodes and Pepper Potts Were Avengers?.
Mark Ruffalo as Bruce Banner / Hulk: An Avenger and genius scientist who, because of exposure to gamma radiation, typically transforms into a monster when enraged or agitated. Ruffalo reprises his role as 2012-Hulk, from What If… James Rhodes and Pepper Potts Were Avengers?.
Chris Hemsworth as Thor: An Avenger and the king of Asgard, based on the Norse mythological deity of the same name. Thor now wields a mystical axe known as Stormbreaker, after the destruction of his hammer, Mjølnir. Hemsworth reprises his role as 2012-Thor from What If… James Rhodes and Pepper Potts Were Avengers?.
Lake Bell as Natasha Romanoff / Black Widow: An Avenger and a highly trained spy and former agent of S.H.I.E.L.D. Bell reprises her role as 2012-Natasha Romanoff / Black Widow from What If… James Rhodes and Pepper Potts Were Avengers?.
Jeremy Renner as Clint Barton / Hawkeye: A master archer and a former Avenger and agent of S.H.I.E.L.D. who recently served on house arrest. Renner reprises his role as 2012-Clint Barton / Hawkeye from What If… James Rhodes and Pepper Potts Were Avengers?.
Jon Favreau as Happy Hogan / War Machine: An officer in the U.S. Air Force and Avenger who operates the War Machine armor.
Paul Rudd as Scott Lang / Ant-Man: A former petty criminal and Avenger who acquired a suit that allows him to shrink or grow in scale while also increasing in strength. Jackson A. Dunn voices the character at age 12 while Lee Moore voices the character at age 93.
Chloe Bennet as Daisy "Skye" Johnson / Quake: A former agent of S.H.I.E.L.D., Inhuman, and Avenger with the ability to create earthquakes. Bennet reprises her role from previous MCU media.
Alexandra Daniels as Carol Danvers / Captain Marvel: An ex-U.S. Air Force fighter pilot and Avenger whose DNA was altered during an accident, imbuing her with superhuman strength, energy projection, and flight.
Karen Gillan as Nebula: An adopted daughter of Thanos and Avenger who was raised with Gamora as siblings. Gillan also voices her 2014 variant.
Danai Gurira as Okoye: The general of the Dora Milaje, a group of elite women warriors.
Benedict Wong as Wong: A Master of the Mystic Arts and a companion of Doctor Strange.
Walt Hadfield: An former architect, former head of security at Stark Industries, and Rhodes and Potts' former chauffeur and driver.
Bradley Cooper as Rocket: A member of the Guardians and Avenger who is a genetically engineered raccoon-based bounty hunter, mercenary, and master of weapons and battle tactics.
Josh Brolin as Thanos: An intergalactic warlord from Titan who acquired all six Infinity Stones and triggered the Snap, killing half of all life in the universe.
Benedict Cumberbatch as Dr. Stephen Strange / Doctor Strange: A former neurosurgeon who, after a car accident, discovered the Mystic Arts as a form of healing, discovering magic and alternate dimensions and the Sorcerer Supreme of Kamar-Taj.
Chadwick Boseman as T'Challa / Black Panther: The king of Wakanda, who is the protector of Wakanda, the Black Panther, and gains enhanced abilities by ingesting the Heart-Shaped Herb.
Hudson Thames as Peter Parker / Spider-Man: A teenager, Avenger, and Rhodes and Potts' protégé.
Cynthia McWilliams as Gamora: Nebula's adopted sister and Thanos' adopted daughter seeking redemption for her past crimes. This version is from an alternate 2014.
Elizabeth Olsen as Wanda Maximoff: An Avenger with hypnosis, telekinesis, and reality-warping abilities.
Anthony Mackie as Sam Wilson / Falcon: An Avenger and former U.S. Air Force pararescueman who was given an advanced combat suit by the military.
Sebastian Stan as Bucky Barnes / White Wolf: Rogers' best friend and World War II veteran who was thought killed in action until re-emerging as a brainwashed super-assassin before his programming was removed.
Tom Hiddleston as Loki: Thor's adopted brother, based on the Norse mythological deity of the same name. This version is a variant from 2012.
Pom Klementieff as Mantis: A member of the Guardians of the Galaxy with empathic powers.
Fred Tatascoire as:
Drax the Destroyer: A member of the Guardians of the Galaxy who wants vengeance against Thanos for killing his family.
Corvus Glaive: A member of the Children of Thanos.
Shuri: T'Challa tech-savvy sister who built the vibranium technology for Wakanda.
Thaddeus Ross: The U.S. Secretary of State.
Maria Hill: The former deputy director of S.H.I.E.L.D.
M'Baku: The leader of the Jabari Tribe.
Tom Vaughan-Lawlor as Ebony Maw: A member of the Children of Thanos with dark magic.
Ned Leeds: Parker's best friend and guy in the chair.
Vin Diesel as Groot: A tree-like humanoid and member of the Guardians of the Galaxy.
Brian T. Delaney as Peter Quill / Star-Lord: The half-human, half-Celestial leader of the Guardians of the Galaxy. Delaney also voices 2014-Quill.
Samuel L. Jackson as Nick Fury: The director of S.H.I.E.L.D.
Ross Marquand as Johann Schmidt / Red Skull: The "Stonekeeper" and former World War II Nazi general and leader of Hydra.
Terry Notary as Cull Obsidian: A member of the Children of Thanos.
Kerry Condon as F.R.I.D.A.Y.: The artificial intelligence system that powers Rhodes and Potts' armors.
Carrie Coon as Proxima Midnight: The only female member of the Black Order.
Evangeline Lilly as Hope van Dyne / Wasp: Lang's girlfriend and the daughter of Hank Pym and Janet van Dyne who was handed down the Wasp mantle.
Tessa Thompson as Valkyrie: A member of the Valkyrior and the de facto ruler of the Asgardian refugees' settlement in New Asgard. Thompson reprises her role from previous MCU media.
Rene Russo as Frigga: Thor's mother and the former queen of Asgard. Russo reprises her role from previous MCU media.
John Slattery as Howard Stark: Tony Stark's father and the founder of Stark Industries.
Tilda Swinton as the Ancient One: The previous Sorcerer Supreme of Kamar-Taj and guardian of the Time Stone. Swinton reprises her role from previous MCU media.
Peggy Carter: Rogers' lost love from the 1940s and the director of S.H.I.E.L.D. in the 1970s. A 1970 and 1948 variant appear.
May Parker: Parker's aunt.
Taika Waititi as Korg: A former Kronan gladiator and refugee of New Asgard. Waititi reprises his role from previous MCU media.
Miek: Korg's best friend and a former gladiator from Sakaar.
Angela Bassett as Ramonda: The queen mother of Wakanda and T'Challa and Shuri's mother.
Michael Douglas as Hank Pym: An former entomologist, S.H.I.E.L.D. agent, and physicist who discovered the Pym Particles in the 1960s.
Michelle Pfieffer as Janet van Dyne: Pym's wife and Hope's mother who was stranded in the Quantum Realm for thirty years.
Linda Cardellini as Laura Barton: Clint's wife.
Maximiliano Hernández as Jasper Sitwell: A S.H.I.E.L.D. agent who is an undercover Hydra sleeper agent.
Frank Grillo as Brock Rumlow: A S.H.I.E.L.D. and S.T.R.I.K.E. agent who is an undercover Hydra sleeper agent. Grillo reprises his role from previous MCU media.
Robert Redford as Alexander Pierce: A member of the World Security Council, Fury's superior, and undercover director of Hydra. Redford reprises his role from previous MCU media.
Jack Rollins: A S.H.I.E.L.D. and S.T.R.I.K.E. agent who is an undercover Hydra sleeper agent.
Harley Keener: Rhodes and Potts' former protégé who is now 18 years old.
Kraglin Obfonteri: A member of the Ravagers.
Natalie Portman as Jane Foster: An astrophysicist and Thor's ex-girlfriend.
James D'Arcy as Edwin Jarvis: Stark's chauffeur and driver and the family butler. D'Arcy reprises his role from previous MCU media.
Hiroyuki Sanada as Akihiko: The leader of the Japanese Yukuza. Sanada reprises his role from Avengers: Endgame (2019).
Lexi Rabe as Morgan Rhodes: Rhodes and Potts' 4-year-old daughter. Rabe reprises her role from previous MCU media.
Emma Fuhrmann as Cassie Lang: Lang's 16-year-old daughter who has aged during the five-year period he was in the Quantum Realm. Fuhrmann reprises her role from Avengers: Endgame (2019).
Stan Lee as 1970s car driver: A driver in the 1970s.
Ken Jeong as a security guard: A security guard at the storage unit.
Yvette Nicole Brown as S.H.I.E.L.D. employee: A S.H.I.E.L.D. employee in the 1970s.
Joe Russo as grieving gay man: A grieving gay man who Rogers talks to during a therapy session.
Ava Russo as Lila Barton: Clint's teenage daughter. Russo reprises her role from previous MCU media.
Lia Russo as Hulk fan: A fan of the Hulk. Russo reprises her role from Avengers: Endgame (2019).
Jim Starlin as grieving man: A grieving man.
Howard the Duck: A member of the Ravagers.
Mark Wingert as Tony Stark: The former CEO of Stark Industries and a self-described genius, billionaire, playboy, and philanthropist.