The quest for sustainable, low-cost and environmental friendly engineering materials has increased the application of natural fiber-reinforced polymer (FRP) composite. This paper experimentally investigates the effects of variable mean hemp fiber (HF) aspect ratios (ARs) of 00 (neat), aspect ratios AR_19, AR_26, AR_30 and AR_38 on nano-mechanical (hardness, modulus, elasticity and plasticity), surface and thermal properties of hemp fiber/polycaprolactone (HF/PCL) biocomposites. These biocomposites were characterized by nanoindentation, contact angle, surface energy, thermogravimetric analysis (TGA), thermal conductivity and differential scanning calorimetry (DSC) techniques. After nanoindentation and thermal conductivity tests, the results obtained evidently show that the HF/PCL sample with aspect ratio (AR_26) recorded optimal values. These values include maximum hardness of approximately 0.107 GPa, elastic modulus of 1.094 GPa, and plastic and elastic works of 1.580 and 1.210 nJ, respectively as well as maximum thermal conductivity of 0.2957 W/mK, when compared with other samples. Similarly, the optimal sample exhibits highest main degradable temperature and degree of crystallinity of 432 ℃ and 60.6%, respectively. Further results obtained for the total surface energies and contact angles of these samples with glycerol and distilled water are significant for their materials selection, design, manufacturing and various applications.