Amiet’s theory offers an efficient and accurate means of predicting trailing edge and leading edge noise, but it assumes that the edge is straight and cannot be applied to serrated edges. Serrations are known to be effective at reducing trailing edge and leading edge noise, but little theoretical work has been carried out on predicting the amount of noise reduction. A recently developed model that generalises Amiet’s theory for trailing edge noise with sawtooth trailing edges predicts noise reduction levels of 5-10 dB that are close to experimental measurements. Such generalised Amiet’s theory has yet to be developed for serrated leading edges. There is currently no analytical model that is applicable to serrated leading edges, and such model could play a key role in the design of quieter turbofan engines. This paper derives a generalised Amiet model for predicting leading edge noise with a sawtooth leading edge and validates the noise prediction against experimental results. This work will shed light into the noise reduction mechanism due to serrated leading edges and will help design more effective serrations.