In this study, we built a novel handheld array photoacoustic probe by integrating multiple optical components with a transrectal ultrasound (TRUS) transducer array. The optical components deliver laser energy and TRUS is used for photoacoustic signal detection. Compared to the previously reported probe, the new photoacoustic probe utilizes an optimized light illumination scheme to enhance the utilization-efficiency of the laser energy, thus improving the imaging sensitivity of the probe. In addition, the new probe is compact and easy to handle for clinicians. We validated the use of this photoacoustic probe for prostate cancer imaging through both phantom studies and in vivo canine model study, which mimics the prostate cancer conditions. The results showed that the probe is suitable for clinical use and can be used in the clinics for several potential clinical applications, including early diagnosis of prostate cancer, targeted image-guided biopsy, and image-guided intra-operative procedure.