Volcanic ejecta or lahar can serve as an inorganic support for the immobilization of invertase. Pampanga and Bicol lahar samples were pretreated by ignition at 550 o C for 5 hrs followed by concentrated hydrochloric acid treatment, activated by reaction with aminopropyltriethoxysilane (APTS) and then covalently bound to invertase using glutaraldehyde as linker. Chemical tests confirmed the attachment of APTS to lahar and glutaraldehyde to silanized lahar. The quantity of immobilized invertase on Pampanga white, Pampanga black and Bicol black lahar were 98.73%, 96.73% and 84.27%, respectively. Conditions for maximum activity of invertase immobilized on Pampanga white lahar were pH 3.5, 45 o C and 0.3 M sucrose concentration. The K m and V max for free invertase and immobilized invertase on Pampanga white lahar were 2.37 M and 48.75 mmol/min, and 3.88 M and 38.87 mmol/min, respectively. Invertase bound to Pampanga white lahar was most stable towards repeated and continuous use and towards storage with intermittent use as indicated by its relatively greater activity.