The skull is a complementary combination of flat bones joined by connective suture tissues. Although brain growth produces mainly quasi‐static tension loads across the sutures, physiological loads could produce an alternate combination of tension‐compression, thus tension test looks to be the best way of estimate differences in the biomechanical behavior of sutures. We hypothesized that, [1] the mechanical properties of sutural tissue in the America alligator ( Alligator mississippiensis ) changed during ontogeny, and [2] there were sex‐based difference in the change during ontogeny. Modulus of elasticity (E), and maximum normal elastic stress (σ y ) were evaluated by using a tension test technique in three different mandibular sutures and a control group of mandibular cortical tissue. 67 specimens were removed from 15 subject (8 males and 7 females) covering three ontogenetic groups: [1] juvenile from 12–36 in. long, [2] junior adult from 37–72 in. long, and [3] senior adult from 73–96 in. long. Results demonstrated that there were no significant differences in mechanical properties between male (E=12.87 ± 15.79 MPa) and female animals (E=12.41 ± 13.55 MPa). However, there were significant differences in elastic modulus between specimens from juvenile group and specimens from adult age groups ( p <0.05). In addition, there are statistical differences not only between the control group and the specimens including sutures, but also among sutural positions. In conclusion, mechanical properties are associated with physiological conditions that could affect sutural function, and some mechanical properties in mandibular sutures decrease during ontogeny, suggesting a direct effect of mineralization processes in mechanical properties. Grant Funding Source : Supported by NSF BCS‐0725183, and COLCIENCIAS (Bogotá, Colombia)