The use of passive infrared thermography comprises great opportunities to improve understanding the fatigue damage process of crack-patched structures. Quasi-static and cyclic coupon tests are performed using metallic specimens with single-sided bonded patches and monitored with passive infrared thermography. Different test setups help to differentiate between metallic crack growth and adhesive damage on thermal images. Results show that metallic crack growth can be monitored from the patched side, also in combination with local delamination at the patch/metal interface. Thus, it is possible to analyse the overall degradation progress of the crack patched component under loading conditions and thereby to identify the driving damage mechanism of the particular repair configuration. Being able to understand the overall damage behaviour of crack patched components is essential to improve the ability of predicting its long-term behaviour.