We have developed an integrated photoacoustic imaging (PAI) and high-intensity focused ultrasound (HIFU) system for solid tumor treatments. A single-element, spherically focused ultrasonic transducer, with a central frequency of 5 MHz, was used to induce HIFU lesions in soft tissue. The same ultrasonic transducer was also used as a detector during PAI to guide HIFU ablation. The use of same transducer for PAI and HIFU can reduce the requirement on acoustic windows during the imaging-guided therapy, as well as ensuring the correct alignment between the therapeutic beam and the planned treatment volume. During an experiment, targeted soft tissue was first imaged by PAI. The resulted image was used to plan the subsequent HIFU ablation. After the HIFU ablation, targeted soft tissue was imaged again by PAI to evaluate the effectiveness of treatments. Good contrast was obtained between photoacoustic images before and after HIFU ablation. In conclusion, our results demonstrated that PAI technology may potentially be integrated with HIFU ablation for image-guided therapy.