The elastic properties of cells are important for many of their functions, however the development of label free noninvasive cellular elastography method is a challenging topic. We present a novel single-cell all-optical coherence elastography method that combines optical tweezers producing mechanical excitation on the cell membrane or organelle and phase-sensitive optical coherence microscopy measuring sample response and determining its mechanical properties. The method allows living cells imaging with a lateral resolution of 0.5 μm and an axial resolution up to 10 nm, making it possible to detect nanometer displacements of the cell organelles and to record the propagation of mechanical wave along the cell membrane in response to optical tweezers excitation. We also demonstrate applicability of the method on single living red blood cells, yeast and cancer cells. The all-optical nature of the method developed makes it a promising and easily applicable tool for studying cellular and subcellular mechanics in vivo.