The development of new thermal barrier coatings (TBC's) capable of increasing the efficiency of gas-powered turbines requires an understanding of how the tensile behaviour and ductile to brittle transition temperature (DBTT) of MCrAlY bond coats are influenced by the coating microstructure. In this study, small punch tensile (SPT) tests were conducted on two high velocity oxy-fuel (HVOF) NiCoCrAlY coatings. Both coatings, referred to as BC1 and BC2, comprised a BCC β-NiAl matrix with FCC γ-Ni and TCP σ-Cr2Co secondary phases. Coating BC2 also contained FCC γ′-Ni3Al. Small punch tensile (SPT) tests were conducted on the coatings between RT and 750 °C. The DBTT's of coatings BC1 and BC2 were found to be 600–700 °C and 650–750 °C respectively. Lower phase fractions of γ-Ni were shown to increase the DBTT. The main mode of crack propagation in both coatings was intergranular fracture along the grain boundaries of differing phases. Schematic models were used to demonstrate the change in tensile behaviour across the DBTT and explain the influence of the coating microstructure on the fracture behaviour of both coatings.