Sulfated zirconia (SZ), a solid acid with acid strength comparable to sulfuric acid, has been studied for triglyceride (TG) transesterification and free fatty acid (FFA) esterification using both model compounds and soybean oil (SBO). Even though SZ is one of the most promising solid acid catalysts for esterification of FFAs, the potential of SZ for direct transesterification of TGs remains unexplored. Under the right reaction conditions, SZ can be a suitable catalyst for the synthesis of biodiesel from low grade lipid feedstocks with high concentrations of FFAs given its ability to catalyze both esterification and transesterification. The use of a model TG compound, tricaprylin (TCP), with saturated fatty acid moieties containing eight carbons each (about half the size of a typical TG as found in SBO), allowed us to study how molecular size and chain unsaturation affected catalyst activity and catalyst deactivation. Good TCP conversion (80%) was obtained after 2 h of reaction using SZ (10 wt% based on TG content; 12:1 methanol:TG molar ratio) at 120°C. Higher reaction temperatures resulted in better reaction kinetics and conversions. However, the elevated increase in methanol vapor pressure with reaction temperature becomes a deterrent for the use of temperatures above 150°C. Under the same reaction conditions, esterification was faster than transesterification for reactions where both TGs and FFAs were present. The irreversible adsorption (and possible surface reaction) of large lipid species appears to be strongly linked to catalyst deactivation. Catalyst regeneration studies showed that calcination temperatures below 600°C are preferable to avoid the lost of surface active sulfate groups that can lead to the irreversible lost of catalyst activity.