Like　their　biogenic　counterparts,　synthetic　minerals　with　hierarchical　architectures　should　exhibit　multiple　structural　functions,　which　nicely　bridge　the　boundaries　between　engineering　and　functional　materials.　Nevertheless,　design　of　bioinspired　mineralization　approaches　to　thin　coatings　with　distinct　micro/nanotextures　remains　challenging　in　the　realm　of　materials　chemistry.　Herein,　a　general　morphosynthetic　method　based　on　seeded　mineralization　was　extended　to　achieve　prismatic-type　thin　CaCO3　coatings　on　fibrous　substrates　for　oil/water　separation　applications.　Distinct　micro/nanotextures　of　the　overlayers　could　be　obtained　in　mineralization　processes　in　the　presence　of　different　soluble　(bio)macromolecules.　These　hierarchical　thin　coatings　therefore　exhibit　multiple　structural　functions　including　underwater　superoleophobicity,　ultralow　adhesion　force　of　oil　in　water,　and　comparable　stiffness/strength　to　the　prismatic-type　biominerals　found　in　mollusk　shells.　Moreover,　this　controllable　approach　could　proceed　on　fibrous　substrates　to　obtain　robust　thin　coatings,　so　that　a　modified　nylon　mesh　could　be　employed　for　oil/water　separation　driven　by　gravity.　Our　bioinspired　approach　based　on　seeded　mineralization　opens　the　door　for　the　deposition　of　hierarchical　mineralized　thin　coatings　exhibiting　multiple　structural　functions　on　planar　and　fibrous　substrates.　This　bottom-up　strategy　could　be　readily　extended　for　the　syntheses　of　advanced　thin　coatings　with　a　broad　spectrum　of　engineering　and　functional　constituents.　©　2018　American　Chemical　Society.