Provided is a method for producing a hydroxyalkyl alkyl cellulose having high thermal gel strength while suppressing a reduction in thermal gelation temperature. More specifically, provided is a method for producing a hydroxyalkyl alkyl cellulose including steps of: mixing cellulose pulp with a first alkali metal hydroxide solution to obtain alkali cellulose, reacting the alkali cellulose with an alkylating agent and a hydroxyalkylating agent to obtain a first reaction product mixture, adding a second alkali metal hydroxide solution to the first reaction product mixture without further adding any of alkylating and hydroxyalkylating agents to obtain a second reaction product mixture, and subjecting the second reaction product mixture to purification to obtain a hydroxyalkyl alkyl cellulose.