AIM: Fibroblast growth factor 23 (FGF23) and α-Klotho have been recently identified to play a crucial role in calcium/phosphate metabolism. We herein investigated the possible relation between serum FGF23/α-Klotho levels and coronary artery calcification (CAC) and aortic valve calcification (AVC). METHODS: Among subjects with diagnosed or suspected coronary artery disease (CAD), CAC and AVC were estimated via the Agatston score of 320-detector computed tomography images, and serum FGF23 and α-Klotho levels were measured. RESULTS: In total, 157 subjects were enrolled (75 women and 82 men). We performed logistic regression using CAC as a dependent variable; the highest FGF23 tertile (＞ 52.5 pg/mL) was significantly positively associated with CAC with an odds ratio of 6.61 versus the lowest FGF23 tertile (＜ 35.3 pg/mL) in women after the adjustment for potential confounding variables including age, renal function, hypertension, statin use, diuretic use, and calcium/phosphate metabolism related factors. In addition, the highest α-Klotho tertile (＞ 561 pg/mL) was significantly associated with AVC with an odds ratio of 6.31 versus the lowest α-Klotho tertile (＜ 306 pg/mL) in men after adjusting for the same variables. On the other hand, the association between FGF23 and CAC/AVC in men or that between α-Klotho and CAC/AVC in women was nonsignificant. CONCLUSION: Among subjects with diagnosed or suspected CAD, serum FGF23 was positively associated with CAC in women and serum α-Klotho was positively associated with AVC in men independent of the confounding variables, including the renal function and calcium/phosphate metabolism-related factors.