Langendorff perfused hearts have been frequently studied in recent years using optical fluorescence imaging. This in vitro approach, which enables the heart to continue beating after extraction from the body of the animal, allows investigation of physiological functions with relative simplicity compared to in vivo setups. For example, when combined with voltage- and calcium- sensitive dyes, optical mapping of transmembrane potential, calcium transients, and other parameters can lead to a better understanding of cardiac mechanisms underlying heart failures and diseases. However, biomedical optical imaging is fundamentally limited to superficial investigations due to light scattering in tissues, restricting mapping to the heart surface only. The ability to visualize the heart septum would be important for comprehensive cardiac research. While 3D ultrasound can offer imaging of the entire heart, it can only provide mechanical contrast and the spatio-temporal resolution is also insufficient for imaging the heart in 3D on a beat-by-beat basis. Herein, we investigate on the capabilities of optoacoustic tomographic imaging of the Langendorff heart. The heart isolation method allows direct imaging without the presence of surrounding tissues and reduced blood content, significantly improving the penetration depth as well as image quality. The imaging system can acquire 3D images of the heart with optical contrast at an imaging rate of 100 Hz and 150 µm resolution. This enables capturing beat-by-beat heart motion with temporal resolution of 33 sampling instances per heartbeat. The high spatial resolution also allows identifying important internal heart features, including the septum, valves, cordae tendineae, and papillary muscles.