Biosorption of Cu (II) ions from aqueous solutions onto soursop (Annona muricata L) leaves powder was investigated in a batch system. Several variables such as effect of pH, contact time, concentration of metal ions and biosorbent dosage have been investigated. The result showed that the adsorption process was strongly dependent with pH and initial concentration of Cu (II). The optimum condition was achieved for adsorption on pH 7 and initial concentration of Cu (II) was 500 mg/L with sorption capacity 6.14 mg/g. The optimum adsorption was also achieved with biosorbent dosage 0.25 g and contact time 90 minutes. The experimental equilibrium biosorption data were analyzed by Langmuir isotherm model with R2 = 0.9689. Furthermore, the biosorbent was characterized by Fourier Transform Infra Red (FT-IR) spectroscopy to identify the various functional groups contributing in the sorption process. Scanning Electron Microscope (SEM) was used for surface analysis before and after adsorption process.