Thin film composite membranes on polyolefin structures may be prepared by interfacial polymerization on a polyolefin support. Polyolefin structures may have hollow and/or solid portions. The polyolefin structure may be hydrophilized prior to interfacial polymerization. The hydrophilized structure may also be treated with an aqueous monomer containing solution first, followed by the organic monomer containing solution. Alternatively, an organic monomer solution may be introduced first, followed by the aqueous monomer containing solution when treating a hydrophilized structure. The formed membrane may possess advantageous characteristics, including stability, hydrophilicity, predetermined pore sizes and/or solvent resistance.