Combining functional optical contrast with high spatiotemporal resolution, photoacoustic computed tomography (PACT) benefits mainstream cardiac imaging modalities for preclinical research. However, PACT has not revealed detailed vasculature or hemodynamics of the whole heart without surgical tissue penetration. Here, we present non-invasive imaging of rat hearts using the recently developed three-dimensional PACT (3D-PACT) platform. 3D-PACT utilizes optimized illumination and detection schemes to reduce the effects of optical attenuation and acoustic distortion through the chest wall, thus visualizing cardiac anatomy and intracardiac hemodynamics within a 10-second scan. We then applied 3D-PACT to investigate different structural and functional variations in healthy, hypertensive, and obese rat hearts. 3D-PACT provides high imaging speed and nonionizing penetration to capture the whole heart for diagnosing animal models, holding promises for clinical translation to human neonatal cardiac imaging without sedation or ionizing radiation.