Regression testing makes sure that upgradation of software in terms of adding new features or for bug fixing purposes should not hamper previously working functionalities. Whenever a software is upgraded or modified, a set of test cases are run on each of its functions to assure that the change to that function is not affecting other parts of the software that were previously running flawlessly. For achieving this, all existing test cases need to run as well as new test cases might be required to be created. It is not feasible to reexecute every test case for all the functions of a given software, because if there is a large number of test cases to be run, then a lot of time and effort would be required. This problem can be addressed by prioritizing test cases. Test case prioritization technique reorders the priority in which test cases are implemented, in an attempt to ensure that maximum faults are uncovered early on by the high priority test cases implemented first. In this paper we propose an optimized test case prioritization technique using Ant Colony Optimization (ACO) to reduce the cost, effort and time taken to perform regression testing and also uncover maximum faults. Comparison of different techniques such as Retest All, Test Case Minimization, Test Case Prioritization, Random Test Case Selection and Test Case Prioritization using ACO is also depicted.