In this article, poly(ε-caprolactone)–poly(ethylene glycol)–poly(ε-caprolactone) (PCL–PEG–PCL, PCEC) nanoparticles were successfully prepared for honokiol delivery in vitro. Blank or honokiol loaded PCL–PEG–PCL nanoparticles were prepared in moderate condition by solvent diffusion method without using any surfactants. The prepared blank PCL–PEG–PCL nanoparticles are mono-dispersed and smaller than 200 nm. The particle size increased with increase in polymer concentration and oil–water (O/W) ratio. The prepared PCL–PEG–PCL nanoparticles (40 mg/mL, ca. 106 nm) did not induce hemolysis in vitro. And the 50% inhibiting concentration (IC50) of it (48 h) on HEK293 cells was higher than 5 mg/mL. Honokiol could be efficiently loaded into PCL–PEG–PCL nanoparticles and released from these nanoparticles in an extended period in vitro. After honokiol (HK) was entrapped into PCL–PEG–PCL nanoparticles, the particle size increased with the increase in HK/PCEC mass ratio in feed, and the encapsulated honokiol retained potent anticancer activity in vitro. The PCL–PEG–PCL nanoparticle was suitable for honokiol delivery, and such honokiol loaded PCL–PEG–PCL nanoparticle was a novel honokiol formulation.