The addition of clay mineral fillers in polymeric materials is a great industrial strategy. Among the existing clay minerals, some have remarkable characteristics like attapulgite (ATP). Despite its excellent properties, ATP, being a clay mineral, has many impurities in its structural channels. Therefore, it is necessary to remove the organic matter and other minerals, that is, it is necessary to purify the ATP (acid activation process). Also, in general, inorganic materials do not have good interfacial interaction with organic polymers. Aiming to improve the interaction of ATP with polymeric materials, in addition to acid activation, it is desirable to perform a surface modification of ATP. As this clay mineral has a large cation exchange capacity, it is possible to carry out organophilization by cation exchange. Therefore, the main objective of this work is to study of ATPo on the mechanical properties of HDPE/ATP nanocomposites.