We investigate waveguide efficiency of CsPbI3 microwire waveguides and their photodegradation over a range of continuous wave laser excitation energies and intensities. Under modest laser input intensities <1 kW cm−2 we observe a wavelength dependent efficiency of light propagation in the waveguides. At increased power densities and wavelengths of 473 nm or shorter, microwires undergo photoablation into discrete fragments. Use of diffraction-limited excitation allowed localised cleavage of the microwires with observation of transient photoluminescence from degradation products. TEM analysis of the microwires revealed transformation from the yellow δ-phase to amorphous phases in the region of the photodamage with a degraded morphology consistent with efficient thermal transfer and induced melting.