The results of a study of the permittivity ε΄ and the third harmonic coefficient γ3ω of diisopropylammonium iodide (DIPAI), embedded in porous glass with a pore size of ∼100 nm, are presented. For DIPAI in pores, the temperature of the lower phase transition upon heating increases by 5 K, compared to bulk DIPAI, and is 368 ± 1 K. The upper phase transition is not observed up to 450 K, which is close to the melting point of DIPAI (∼453 K). Upon cooling, one phase transition is observed at a temperature of 364 ± 1 K.