We use Gemini GMOS-IFU observations of three luminous nearby Seyfert galaxies (Mrk 79, Mrk 348, and Mrk 607) to estimate the electron temperature (Te) fluctuations in the inner 0.4-1.1 kpc region of these galaxies. Based on Te determinations through the [O III]λ5007/λ4363 emission line ratio of each spaxel, temperature variations are quantified by computing the integrated value of the temperature fluctuation parameter (t2) projected in the plane of the sky $t_{\rm A}^{\rm 2}$, for the first time in active galactic nuclei (AGNs). We find $t_{\rm A}^{\rm 2}$ values of 0.135, 0.039, and 0.015 for Mrk 79, Mrk 348, and Mrk 607, respectively, which are of the same order or larger than the maximum values reported in star-forming regions and planetary nebulae. Taking into account that $t_{\rm A}^{\rm 2}$ should be considered a lower limit of the total t2 in the nebular volume, the results suggest that the impact of such fluctuations on chemical abundance determinations can be important in some AGNs.