Saddlebag Lake Pendant (SLP), a zone of hydrothermally-altered, Ordovician-Cretaceous metasedimentary and metavolcanic rocks intruded by the Cretaceous Tuolumne Intrusive Complex (TIC) in California’s Sierra Nevada, was deformed by the Cretaceous Sierra Crest Shear Zone (SLSZ). Unlike other Sierra Nevada pendants, both δ¹⁸O and δD values from SLP show great variability, with most samples in isotopic disequilibrium. Mineral δ ¹⁸O and δD values range from –1.5‰ to +16.1‰ and –140‰ to –67‰, respectively. All TIC isotopic compositions indicate normal magmatic values. Most Paleozoic units record internally-generated metamorphic fluids. Jurassic metasedimentary and Triassic metavolcanic rocks have great isotopic variability with calculated fluid δ ¹⁸O and δD values that range from –2.6‰ to +15.2‰, and –106‰ to –25‰, respectively. All low isotope values are from the SLSZ at Sawmill Canyon. Isotopic data suggests these units were affected by magmatic waters generated by TIC crystallization, and subjected to localized infiltration of meteoric-hydrothermal fluid at Sawmill Canyon.