Magnetic　nanocomposites　were　fabricated　by　attaching　surface-modified　magnetite　nanoparticles　to　the　surface　of　reduced　graphene　oxide　(rGO)　in　this　study.　By　applying　an　external　magnetic　field,　the　rGO　were　highly　aligned　in　the　cement　paste.　The　orientation　factor　of　aligned　rGO　was　found　to　be　0.71　by　analyzing　the　polarized　Raman　scattering　spectra.　The　alignment　of　the　rGO　contributed　to　both　the　mechanical　and　dielectric　properties　of　the　cement　paste.　The　flexural　strength　of　the　specimen　with　aligned　rGO　improved　by　48%　compared　with　that　of　the　cement　pastes　with　randomly　distributed　rGO.　The　dielectric　constant　at　100　Hz　of　the　specimen　with　aligned　rGO　was　increased　by　271%　compared　with　that　of　cement　pastes　with　randomly　distributed　rGO.　A　modified　rule　of　mixtures　was　proposed　to　predict　their　mechanical　and　dielectric　properties.　This　study　offers　insight　on　the　development　of　nanofiller-incorporated　cement-based　materials　with　enhanced　mechanical　and　dielectric　properties.