Purpose: To examine concordance in biometry, keratometry, and intraocular lens (IOL) calculation between the Heidelberg Anterion Cataract App and the Zeiss IOLMaster 700 in a US population presenting for cataract evaluation. Methods: In this retrospective cross-sectional study, 64 eyes of 40 patients presenting for cataract evaluation underwent imaging with both devices. Agreement was assessed for axial length (AL), anterior chamber depth (ACD), lens thickness (LT), white-to-white distance (WTW), central corneal thickness (CCT), pupil diameter (PD), and anterior, posterior, and total keratometry using Lin’s concordance correlation coefficient (CCC), Bland–Altman analysis and generalized estimating equations. Non-toric and toric IOL calculations were performed with the Barrett Universal II and Barrett True-K Toric formulas, respectively. Results: Concordance was excellent for AL, ACD, LT, and CCT (CCC > 0.980), with no significant difference in AL. Compared with IOLMaster 700, Anterion measured larger PD (+0.56 mm), deeper ACD (+0.07 mm), thicker LT (+0.07 mm), thinner CCT (−3.19 μm), and smaller WTW (−0.22 mm; all p < 0.01). Anterior keratometry showed excellent concordance (CCC ≥ 0.980) despite small flatter offsets in average K, K1, K2 and difference in (Δ)K (−0.13, −0.08, −0.16 D, −0.10). Concordance was poor for posterior keratometry (average K: CCC = 0.529; Anterion steeper by 0.34 D), fairly good for total keratometry (average K: CCC = 0.891, Anterion flatter by 0.68 D), and these systematic inter-device offsets may be clinically relevant. For non-toric calculations, unrounded spherical IOL power agreed within 0.50 D in 88.88% (N = 56/63) of eyes and predicted residual refractive error within 0.25 D in 95.24% (N = 60/63). For toric calculations, predicted residual refractive error and residual astigmatism agreed within 0.25 D in 95.16% (N = 59/62) and 85.48% (N = 53/62) of eyes, respectively. Conclusions: Anterion and IOLMaster 700 showed strong agreement in core biometry, anterior keratometry, and predicted refractive outcomes, though posterior and total keratometry differed systematically. Postoperative refractive outcome studies are needed before the devices can be considered interchangeable in routine practice.