This Letter reports a lead (II) ion sensor composed of a tapered multimode fibre (MMF) coated with chitosan. The diameter and length of the tapered fibre region is 20 mu m and 1 cm, respectively. Tapered MMF is used because it is more flexible and compact compared with plastic clad silica. Chitosan is chosen as the sensing layer because it can absorb heavy metal ions due to its unique properties as polyelectrolyte and chelating agent. The refractive index of the chitosan layer changes as it absorbs lead (II) ion and this leads to an increase in the absorbance measured by the spectrophotometer. This is tested by immersing the sensor in a solution that contains lead (II) ion with different concentrations, from 0.2 to 1 ppm. The results show that the absorbance measured by the spectrophotometer increased as the concentration of the lead (II) ion increased. The sensor's average sensitivity is measured as 40.554 abs/ppm. This sensor is simpler compared with surface plasmon resonance-based lead (II) ion sensor because it does not require metal coating prior to the sensing layer coating.