The current methods of cancer treatment don’t focus on the influence of interpatient genetic variations on the treatment outcomes. Genetic variations in the genes which are involved with drug metabolism and targets can affect treatment response and toxicity. In the recent time, many advances have been made to detect such candidate gene variations and use them as biomarkers in predicting the treatment outcomes in colorectal cancer (CRC). CRC remains one of the common causes of worldwide morbidity and mortality. In the last decade, many drugs have been approved including targeted therapies for the management of CRC which lead to improvement in the median survival and overall survival rate. However, there are significant variations in the response rate and toxicity among CRC patients with the current anti-cancer drugs. Interindividual response variations to chemotherapy can be influenced by several factors among them the genetic factor plays a key role. This emphasizes the need for the new genetic biomarkers which enable the selection of optimal drugs to benefit the patient care. This review focuses on single nucleotide polymorphisms which are known to affect the outcome of anticancer drugs used in the management of colorectal cancer.