Photothermal neuromodulation is a promising non-electrical neural stimulation technology for treating brain diseases through optically induced cell membrane temperature changes. However, the technology faces limitations in understanding its mechanism and impact on cellular behavior due to the restriction of directly measuring temperature changes at the cell interface from a very close distance during optical stimulation of neural cells, necessitating advancements in high-precision temperature sensing and electrical recording without light interference. This challenge is addressed by developing ultrasensitive cell membrane interface temperature sensors integrated with low-noise electrical recording capabilities. Transparent resistive temperature detectors, composed of a 10 nm thickness of ultrathin Au film fabricated by polyelectrolyte seed layer-induced thermal evaporation, achieved precise measurement and control of temperature changes without significant light interference and self-heating. A transparent electrode composed of the same ultrathin Au layer shows low-noise electrical recordings of neural signals upon photothermal stimulation. Using this multifunctional system, it is demonstrated that an average increase of 2.34 °C at neuronal cell surfaces results in over 95% suppression of hippocampal neural spike activities. The approach provides unprecedented insights into the mechanisms of photothermal neuromodulation and its effects on cellular behavior, paving the way for advanced treatments of neurological disorders.