Microsensors and -actuators for medical applications have been under research for decades. However, reliable, continuous and economical monitoring in physiological and biological environments (glucose, blood gases and ionic analytes) still remains an unsolved problem, mainly due to host response towards the implant and instability of sensor components in biological electrolytes. Foreign body response and bio-fouling caused by the environment impairs sensor performance due to alteration of the electrodes and delamination of sensor components. We introduce a biostable electrochemical microsensorarray to measure oxygen, pH and electrical impedance in situ to be employed to probe physiological and biological environments. These parameters were chosen for their sensitivity with respect to the composition and properties of biological tissue. Standard thin film and microstructure technology in combination with electrochemical electrode functionalization was used to fabricate all sensors in a small planar array. Oxygen sensor performance showed a sensitivity of 3,31 – 12,8 nA / mg/l and a response time ranging from 10s – 250s. pH measurements showed linear behavior (-73,2 mV/pH) between pH 4-10. All sensors were measured against a commercial reference electrode, while showing similar absolute values, confirming reproducibility in fabrication. In biological and medical applications the microsensorarray enables simultaneous measurements of all sensor parameters. A dedicated potentiostat unit (“MiniPot”) was developed for this purpose.