Photoacoustic sensing and imaging have emerged in the biomedical field and shown great potentials. Miniaturization and multi-functionality are in need for practical sensing scenarios. As a minimal and economical solution, micromachined ultrasound transducers can be implemented into the photoacoustic sensing system. In this work, we present a photoacoustic dual-mode microsensor based on PMUT technique. PMUT has its fundamental resonance and other high-order resonances. It displays high sensitivity for signal detection at the fundamental resonant frequency, and wide bandwidth at its high orders. Taking advantage of PMUT’s frequency-domain characteristic, we propose a dual-mode photoacoustic sensing method from a single received signal. As the preliminary results are shown in the manuscript, such a dual-mode microsensor has the potential to provide biological indicators and healthcare monitoring.