This study introduced hydrophobic silica nanoparticles (SiNPs) into an interface of aqueous and hydrate-forming oil phases and analyzed the inhibition of hydrate crystal growth after seeding the hydrate slurry. The hydrate inhibition performance was quantitatively identified by micro-differential scanning calorimetry (micro-DSC) experiments. Through the addition of 1.0 wt % of SiNPs into the water-oil interface, the hydrate crystal growth only occurred around the seeding position of cyclopentane (CP) hydrate slurry, and the growth of hydrate crystals was retarded. Upon a further increase in the SiNP concentration up to 2.0 wt %, the SiNP-laden interface completely prevented hydrate growth. We observed a hollow conical shape of hydrate crystals with 0.0 and 1.0 wt % of SiNPs, respectively, but the size and shape of the conical crystals was shrunken at 1.0 wt % of silica nanoparticles. However, the conical shape did not appear with an increased nanoparticle concentration of 2 wt %. These findings can provide insight into hydrate inhibition in oil and gas delivery lines, possibly with nanoparticles.