Undertale took about 2.5 to 3 years to make, with commonly cited figures ranging from 32 months to roughly 2 years and 5 months depending on how the development start date is counted.

What that means

  • Toby Fox started work in 2013 and the game released in September 2015.
  • Some sources describe the full development time as 32 months.
  • Others round it to about 2 years and 5 months or simply over 3 years when including early concept and broader development estimates.

Quick scoop

So the simplest answer is: roughly 3 years.