A small fraction (~0.1% — 1%) of the gravitational-wave signals detectable by ground-based detectors are expected to undergo strong gravitational lensing by intervening galaxies and clusters. In addition, compact objects with sizes comparable to the GW wavelength can produce micro-lensing effects that can distort the observed signal. I will talk about how the observation (as well as non-observation) of lensed GWs can probe different aspects of cosmology, including primordial black holes, dark matter and cosmic expansion rate.