This study presents multifunctional inorganic nanoparticles designed for cancer cell-specific delivery of hydrophobic anticancer drugs and dual imaging (optical and MR). The nanoparticles consist of superparamagnetic iron oxide nanocrystals encapsulated within mesoporous silica spheres, which are labeled with fluorescent dyes and coated with hydrophilic groups to prevent aggregation. The mesoporous silica is further modified with fluorescent molecules and targeting ligands, and the pores are filled with chemotherapeutic drug molecules. These nanoparticles can be monitored inside living cells by both MR and fluorescence imaging and are used as a drug delivery vehicle. The targeting ligand modification increases the drug payload delivery into human cancer cells relative to that in non-cancerous cells. The synthetic procedures use inexpensive and non-hazardous precursors and are simple enough for large-scale production. The potential to simultaneously monitor and deliver molecules to the targeted tissue region will be highly beneficial for both imaging and therapeutic purposes. The nanoparticles were synthesized by thermal decomposition of iron-oleate complexes in a solution of oleic acid surfactants and octadecene solvent. The iron oxide nanocrystals were then incorporated into mesoporous silica nanoparticles, which were synthesized by modifying the procedures described by Kim et al. and Fan et al. The mesoporous silica spheres were synthesized around the iron oxide nanocrystals by adding tetraethylorthosilicate (TEOS) into an aqueous solution containing CTAB-coated nanocrystals, CTAB, and sodium hydroxide. The interaction between the hydrolyzed TEOS molecules, the CTAB-coated nanocrystals, and the free surfactant micelles helped promote the base-catalyzed condensation of TEOS to form the mesostructure. The morphology of the iron oxide–mesoporous silica nanoparticles is highly dependent upon the temperature of the solution. The NPs were then functionalized with fluorescent dye molecules using a co-condensation method. The NPs were also modified with hydrophilic trihydroxysilylpropyl methylphosphonate to prevent interparticle aggregation. The NPs were tested for their ability to deliver water-insoluble anticancer drugs into cells and their effectiveness in targeting cancer cells. The NPs were used to store and deliver water-insoluble anticancer drugs into cells. The materials were loaded with either camptothecin (CPT) or paclitaxel (TXL) by soaking them in a concentrated drug–DMSO solution. The drug-loaded NPs were collected by centrifugation to remove the supernatant and dried under vacuum before being resuspended in aqueous solution. The NPs were tested for their ability to target cancer cells using folic acid as the targeting component. The NPs were found to have increased specificity toward cancer cells due to the overexpression of the α-folate receptor on cancer cells. The NPs were also tested for their ability to deliver drugsThis study presents multifunctional inorganic nanoparticles designed for cancer cell-specific delivery of hydrophobic anticancer drugs and dual imaging (optical and MR). The nanoparticles consist of superparamagnetic iron oxide nanocrystals encapsulated within mesoporous silica spheres, which are labeled with fluorescent dyes and coated with hydrophilic groups to prevent aggregation. The mesoporous silica is further modified with fluorescent molecules and targeting ligands, and the pores are filled with chemotherapeutic drug molecules. These nanoparticles can be monitored inside living cells by both MR and fluorescence imaging and are used as a drug delivery vehicle. The targeting ligand modification increases the drug payload delivery into human cancer cells relative to that in non-cancerous cells. The synthetic procedures use inexpensive and non-hazardous precursors and are simple enough for large-scale production. The potential to simultaneously monitor and deliver molecules to the targeted tissue region will be highly beneficial for both imaging and therapeutic purposes. The nanoparticles were synthesized by thermal decomposition of iron-oleate complexes in a solution of oleic acid surfactants and octadecene solvent. The iron oxide nanocrystals were then incorporated into mesoporous silica nanoparticles, which were synthesized by modifying the procedures described by Kim et al. and Fan et al. The mesoporous silica spheres were synthesized around the iron oxide nanocrystals by adding tetraethylorthosilicate (TEOS) into an aqueous solution containing CTAB-coated nanocrystals, CTAB, and sodium hydroxide. The interaction between the hydrolyzed TEOS molecules, the CTAB-coated nanocrystals, and the free surfactant micelles helped promote the base-catalyzed condensation of TEOS to form the mesostructure. The morphology of the iron oxide–mesoporous silica nanoparticles is highly dependent upon the temperature of the solution. The NPs were then functionalized with fluorescent dye molecules using a co-condensation method. The NPs were also modified with hydrophilic trihydroxysilylpropyl methylphosphonate to prevent interparticle aggregation. The NPs were tested for their ability to deliver water-insoluble anticancer drugs into cells and their effectiveness in targeting cancer cells. The NPs were used to store and deliver water-insoluble anticancer drugs into cells. The materials were loaded with either camptothecin (CPT) or paclitaxel (TXL) by soaking them in a concentrated drug–DMSO solution. The drug-loaded NPs were collected by centrifugation to remove the supernatant and dried under vacuum before being resuspended in aqueous solution. The NPs were tested for their ability to target cancer cells using folic acid as the targeting component. The NPs were found to have increased specificity toward cancer cells due to the overexpression of the α-folate receptor on cancer cells. The NPs were also tested for their ability to deliver drugs