This study proposes and evaluates a precise and labor-saving method for quantifying phthalic-acid esters (PAEs) in indoor air based on solid-phase extraction. Three different adsorbents were evaluated; i.e., two types of octadecyl silica (ODS) filter and a styrene–divinylbenzene (SDB) copolymer cartridge. Calibration curves for five PAEs [diethyl phthalate (DEP), diisobutyl phthalate, di-n-butyl phthalate (DBP), benzyl butyl phthalate (BBP), and di(2-ethylhexyl) phthalate (DEHP)] were created using an internal standard (DBP-d₄). Values of the coefficient of determination (R²) indicated good linearity of the calibration curves (R² > 0.9953). Among the three adsorbents, the SDB cartridge was easiest to handle because it can be used without cleaning and has the lowest blank value. The recovery of deuterated PAEs (DEP-d₄, DBP-d₄, BBP-d₄, and DEHP-d₄) did not differ significantly among the three adsorbents; values were consistently > 89.7% for an air volume of 2.88 m³. During simultaneous indoor air sampling, PAE concentrations were very similar for the three adsorbents. Interlaboratory validation studies were conducted in five laboratories to validate the proposed method for two PAEs (DBP and DEHP). The mean recoveries of the two PAEs added to two types of adsorbent were 91.3–99.9%, the reproducibility relative standard deviations (RSD_R) were 5.1–13.1%, and the Horwitz ratio (HorRat) values were 0.31–0.79. The proposed method using solid-phase extraction with two types of adsorbents provides accurate estimates of PAEs in ambient air.