Ignition delay times of iso-butanol with fuel concentration of 0.5-1.0% were measured behind reflected shock waves. The experiments were conducted in the temperature range of 900-1700 K, at pressures of 1.2-10.0 atm and equivalence ratios of 0.5-2.0. The measured ignition delay times were compared with previous data under the same conditions and were correlated through multiple linear regression. Using the correlation, the ignition delay times of iso-butanol were compared to those of n-butanol. It was found that iso-butanol presented longer ignition delay time than that of n-butanol. Three available models were used to simulate the ignition delay times. Results showed that Sarathy model exhibited the best predictions at high temperature, but none of these models could well reproduce the measured ignition delay times at intermediate low temperature. Reaction pathway analysis was performed to chemically interpret the observed difference in ignition delay times of n-butanol and iso-butanol. In addition, sensitivity analysis was made to ascertain the key reactions that control the intermediate low temperature ignition in the Sarathy model.