Objective To verify the validity of the body adiposity index (BAI) in a sample of Costa Rican students. Methods Volunteers were 93 females (mean age = 18.6 ± 2.4 years) and 106 males (mean age = 19.2 ± 2.8 years). Dual‐energy X‐ray absorptiometry (DXA) was used as the “gold standard” to determine body fat percentage (BF%). Pearson's correlation coefficient and paired samples t‐test studied the association and mean differences between BAI and DXA BF%. Concordance between BAI and DXA BF% was determined by the Lin's concordance correlation coefficient and the Bland‐Altman agreement analysis. Results Significant correlations between BAI and DXA BF% were found for females (r = 0.74) and males (r = 0.53) (P < 0.001). Differences between methods were found for females (BAI = 29.3 ± 4.1% vs. DXA = 36.5 ± 7.9%) and males (BAI = 24.8 ± 3.7% vs. DXA = 21.9 ± 8.6%; P < 0.001). Concordance was poor in females and males. Bland‐Altman plots showed BAI underestimating and overestimating BF% in relation to the “gold standard” in females and males, respectively. Conclusions BAI presented low agreement with BF% measured by DXA; therefore, BAI is not recommended for BF% prediction in this Central American sample studied. Am. J. Hum. Biol. 28:394–397, 2016. © 2015 Wiley Periodicals, Inc.