A physiologically stable thiolate gold(I) derivative [Au(Spyrimidine)(PTA-CH2Ph)]Br has shown inhibition in colon cancer proliferation of Caco-2/TC7, Caco-2/PD7 and HTC-116-luc2 cell lines via apoptotic pathway and S-phase arrest in the cell cycle. Intraperitoneal injection of [Au(Spyrimidine)(PTA-CH2Ph)]Br in athymic nude mice inoculated with HTC-116-luc2 cells prolonged their survival and greatly inhibited tumour growth, near to disappearance. Low concentration of gold in urine and blood were detected in mice after 48 h of administration of 5 mg/kg body weight (bw) of the gold complex and non-organ (kidney and liver) damage has been detected after gold treatment. The results obtained suggested that the thiolate gold(I) derivative shown here could be considered as a candidate for therapeutic treatment in colon cancer.