In Puerto Rico, the slick hair genotype/phenotype has been shown to increase heat tolerance and milk yield in mature dairy cows. However, it is unknown if this superior thermoregulatory capacity may result in growth differences during the post-weaning period. Therefore, this study aimed to evaluate the change in body weight (BW) over time of 25 Puerto Rican Holstein heifers with regular (WT; n = 14) or slick (SL; n = 11) haired coats. Hair coat types were first chosen visually and then genomically confirmed. The heifers studied were born from October 21, 2013 to February 14, 2015, weaned at 60 d of age, and weighed monthly from 4 to 34 mo of age. Data were analyzed by the GLIMMIX, GLM, and REG procedures of SAS. Hair coat type and age interacted to affect BW (P = 0.0005). However, no differences were observed in BW between the WT and the SL heifers (mean values over the 30 mo of 279.33 ± 5.78 and 275.06 ± 6.91 kg, respectively; P = 0.3182); and as age progressed from 4 to 34 mo, BW increased in both, the WT and the SL heifers (93.52 ± 11.42 to 446.35 ± 28.27 kg and 85.69 ± 9.97 to 381.37 ± 35.81 kg, respectively; P < 0.0001). The coat type by age interaction may be explained by the fact that in the WT heifers the growth curve was best described by the linear regression BW = 12.28 age + 54.41 (R² = 0.88; P < 0.0001); while in their SL counterparts, it was best explained by the quadratic regression BW = −0.32 age² + 22.75 age + 6.24 (R² = 0.74; P < 0.0001). These different growth curves suggest that, under our conditions, the SL heifers may reach earlier and smaller mature body weights than their WT counterparts. Therefore, future studies should evaluate any possible differences in mature body weight or age at maturity between both hair coat types.