The purpose of this study was to conjugate Trastuzumab with fluorine-bearing PAMAM dendrimer to compare activities in three-dimensional (3D) cultured breast cancer cells with parent Trastuzumab. An in vitro study was performed to determine cellular responses to fluorinated Trastuzumab conjugates by Magnetic Resonance Imaging (MRI). Breast cancer cells were cultured in 3D geometry. Proton ( 1 H) MRI and Fluorine-19 ( 19 F) MRI were used for visualization of cellular locations within a Hollow Fiber Bioreactor (HFBR) device and to monitor the cellular response to treatment. The results of this study confirm that cell growth is significantly decreased following treatment with Trastuzumab conjugates. The use of fluorinated Trastuzumab conjugates decreases breast cancer cell growth in 3D cultures and allows for tracking of drug delivery to cancer cells via 19 F.