Heterodyne micro-interferometry was utilized to measure out-of-plane transient displacements in the interphase due to thermal cycling. In-situ measurements were made on single carbon fiber/epoxy samples with interphases of varying glass transition temperature. Interphase properties were tailored such that one set of samples had fibers which were coated with a low T-g resin, another set had a higher T-g coating, and in the third set the fibers were uncoated. The interferometric data demonstrated that interphase T-g has a significant effect on the rate and magnitude of the thermal deformations at the fiber/matrix interface. The presence of a low T-g interphase caused an increase in the magnitude of the thermal displacements due to a local softening of the matrix and increase in coefficient of thermal expansion. In addition, the rate at which the displacements increase was also higher due to the reduction in T-g. Samples with untreated fibers (no tailored interphase) behaved as if a low T-g interphase had formed. Experimental displacement profiles were also compared with finite element predictions to assess the behavior of the tailored interphases.