Val Kilmer, recovering from throat cancer, was unable to reprise his role as Madmartigan, so his son Jack Kilmer voiced the character's cameo appearances, having previously duplicated his father's voice in the 2021 documentary Val.

Although he had lost full use of his vocal cords due to throat cancer, Val Kilmer still initially recorded Madmartigan's lines, which were used as a guide track for his son Jack to replicate.

Talisa García was cast as Queen Arianna in April 2022, marking the first time a transgender actor appeared in a Lucasfilm production.

Cailee Spaeny was originally cast in the role that ultimately went to Ruby Cruz, with the recasting confirmed in March 2021.

Discussions about a Willow continuation date back to 2005, when George Lucas mentioned Lucasfilm's return to television at Celebration III, while Warwick Davis repeatedly expressed interest in a sequel in later interviews.

The series went through multiple pilot directors: Jon M. Chu departed due to production delays and personal reasons, his replacement Jonathan Entwistle also exited following delays caused by recasting, and Stephen Woolfenden ultimately directed the first two episodes.

Filming took place mainly in Wales starting June 2021, using Dragon Studios near Llanharan, where five stages totaling 28,000 square feet and a six-acre set for Tir Asleen Castle were built.

The production built a set for the 'Immemorial City' at Dragon Studios that drew inspiration from Blade Runner 2049, and constructed 20 additional buildings for creature creation, puppeteering, special effects, and costumes with extra space and ventilation to comply with COVID-19 guidelines.

Beyond Dragon Studios, the crew filmed at 32 locations across Wales, including Pendine Sands, Morlais Quarry, Merthyr Mawr, Neath Abbey, Snowdonia, and Holyhead, with Creative Wales funding 25 trainees and Lucasfilm hiring 335 full-time crew members, 206 of them Welsh citizens.

The series score was composed by James Newton Howard and Xander Rodzinski and incorporates themes from the original 1988 film written by James Horner.

Despite generally favorable reviews (84% on Rotten Tomatoes, 70 on Metacritic) and strong streaming numbers, Disney+ cancelled Willow after one season in March 2023 amid broader cost-cutting, and removed it entirely from the platform on May 26, 2023.