Magnesium-aluminum-chloride-layered double hydroxides (MgAl-Cl-LDHs) intercalated with low molecular weight heparin (LMWH) were prepared for the first time by the coprecipitation method and then characterized by XRD, elemental analysis, FTIR, SEM, and TEM. MgAl-LDH was studied as the drug carrier for LMWH, a widely used anticoagulant, in order to overcome some of its pharmaceutical limitations, such as its short half-life. In vitro release tests of LMWH-LDH in pH 7.4 PBS at 37 °C show a biphasic and sustained profile of LMWH anion release with ∼20% in the first 12 h and another ∼20% in the following 108 h. After release, the residue was characterized and dissolution−diffusion kinetic models fitted. The mechanism of MgAl-LMWH-LDH release is probably due to surface diffusion and bulk diffusion via anionic exchange of LMWH anions on or in the LDH with anions in the PBS solution.