The present work reports on a graphene-like material that is promising for photodetection applications due to its high optical absorption and layer-dependent properties. To date, only narrowband photodetectors have been realized; therefore, extending the working wavelength is becoming more imperative for applications such as high-contrast imaging and remote sensing. In this work, we developed a novel detection technique that provides enhanced performance across the infrared and terahertz bands by using an antenna-assisted top-gated black phosphorus phototransistor. By using the proposed sophisticated design, the adverse effect due to the back-gate that is generally employed for a long-wavelength photon coupling can be eliminated. Moreover, the antenna-assisted near-field and dark current can be further tailored electromagnetically and electrostatically by employing a gate finger, thus resulting in improved detection efficiency. Various detection mechanisms such as thermoelectric, bolometric, and electron-hole generation are differentiated on the basis of the device geometry and incident wavelength. The proposed photodetector demonstrated superior performance-excellent sensitivity of more than 10 V W-1, a noise equivalent power value of less than 0.1 nW Hz-0.5, and a fast response time across disparate wavebands. Thus, the photodetector can satisfy diverse application requirements.