The understanding of the mechanical behavior of sealants is a prerequisite for the improvement of the integrity and reliability of solid oxide fuel cell stacks. The glass-ceramic sealant material in a SOFC stack is usually a thin layer; hence, micromechanical testing methods need to be applied for characterization. Indentation testing is used in the current study to determine elastic modulus and fracture toughness. The properties of sealant materials in stack typical thin layer geometry are compared with sintered bars. In addition to tests of as-joined material, the effect of stack operation on the properties is assessed.