Renewable nacre-like heparin (HEP)/layered double hydroxide (LDH) ultrathin films were first fabricated via a bottom-up layer by layer (LBL) deposition technique, which simultaneously showed largely enhanced mechanical properties and good blood compatibility. The results of UV-vis, FTIR, XRD and SEM analysis indicate that the HEP/LDH ultrathin films stacked densely together to form a well-defined brick-and-mortar structure. A strong electrostatic and hydrogen bond network at the organic–inorganic interface allowed the modulus of the film reach ca. 23 GPa, which was remarkably enhanced compared to previously reported polymer–LDH hybrid films. Due to the interlamellar heparin, the (HEP/LDH)_n film may prove to be beneficial for new medical applications or as a replacement for conventional petroleum based plastics.