Magnetic nanoparticles (MNPs) have emerged as a promising tool for cancer therapy, providing significant potential for multimodal cancer treatments that include chemotherapy, magnetic hyperthermia, and bioactive targeting. The physicochemical properties of MNPs, including size, surface chemistry, and magnetic properties, play a crucial role in determining their therapeutic effectiveness and overall performance in multimodal cancer therapy. The present study introduces a magnetic nanoformulation (
c
MNP‐mPEG‐Dox‐Ab) nanobioengineered for an integrated therapeutic approach. The cubic‐shaped MNPs (
c
MNP) are functionalized with a biocompatible polymer, mPEG‐NH
2
, to immobilize anti‐HER2 antibody and the anticancer drug doxorubicin. The nanoformulation exhibits a controlled drug release in response to pH and temperature stimuli. Notably, under an alternating magnetic field (AMF), 64% drug release is observed at an acidic pH, which mimics the tumor microenvironment. Cytotoxicity studies on the HCC1954 breast cancer cells reveal that the nanoformulation without an anti‐HER2 antibody induces 25% cell death, which increases to 52% upon conjugation with the anti‐HER2 antibody, confirming the bioactive targeting effect. Apoptosis studies demonstrate a significant increase in the apoptotic cell population under hyperthermic conditions relative to the physiological temperature. This study underscores the potential of
c
MNP‐mPEG‐Dox‐Ab nanoformulation to enhance the precision and therapeutic efficacy of multimodal cancer therapy through bioactive targeting.