Millennial students make up a large portion of undergraduate students attending colleges and universities, and they have a variety of online resources available to them to complete academically related information searches, primarily Web based and library-based online information retrieval systems. The content, ease of use, and required search techniques are different between the two information retrieval systems. Students often prefer searching the Web, but in doing so often miss higher quality materials that may be available only through their library. Furthermore, each system uses different information retrieval algorithms for producing results, so proficiency in one search system may not transfer to another. Web based information retrieval systems are unable to search and retrieve many resources available in libraries and other proprietary information retrieval systems, often referred to as the Invisible Web. These are resources that are not available to the general public and are password protected (from anyone not considered to be an affiliated user of that particular organization). These resources are often licensed to libraries by third party vendors or publishers and include fee-based access to content. Therefore, many millennial students may not be accessing many scholarly resources available to them if they were to use Web based information retrieval systems. Investigation of how millennial students approach searches for the same topic in both systems was conducted. The goal was to build upon theory of why students search using various techniques, why they often choose the Web for their searches, and what can be done to improve library online information retrieval systems. Mixed qualitative methods of data gathering were used to elicit this information. The investigation showed that millennial undergraduate students lacked detailed search strategies, and often used the same search techniques regardless of system or subject. Students displayed greater familiarity and ease of use with Web based IR systems than online library IR systems. Results illustrated suggestions for search design enhancements to library online information retrieval systems such as better natural language searching and easier linking to full text articles. Design enhancements based on millennial search strategies should encourage students to use library-based information retrieval systems more often. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]