Online shopping is a common feature of modern adult life and is made easy with targeted advertisements, a large buy now button, and pre-entered credit card information. However, these features do not support making purchasing decisions based on what is best for the individual. Decision making about buying items requires an understanding of basic mathematics, one's current finances and circumstances, and information about the product, then choosing whether to purchase the item. Adults with intellectual and developmental disabilities (IDD) need explicit instruction on how to make informed decisions regarding online purchases. The current study sought to evaluate the effectiveness of an intervention package consisting of a mnemonic and behavior skills training (BST) delivered remotely to improve the decision making of three adults with IDD when shopping online through a multiple probe across participants design. Inter-observer agreement and procedural fidelity was assessed throughout each phase of the study and social validity interviews were conducted to measure perceptions of participants, parents, and professionals on the importance of the goals, procedures, and outcomes of the study. Results of the study indicated a functional relationship between the intervention package and the dependent variable. All participants acquired the decision-making skills with 100% accuracy across five consecutive sessions by receiving instruction through BST on the use of the CAN-B mnemonic. All participants were also able to maintain at least 86% of the decision making task analysis steps 2, 4, and 6 weeks after the intervention was removed. Participants, parents, and professionals viewed the intervention as socially significant as indicated by survey responses completed before and after the study. Furthermore, the decision-making skills generalized to novel online shopping websites. This study extends previous research demonstrating that adults with IDD can learn to make decisions through an intervention package consisting of BST, a mnemonic, and an Excel spreadsheet. This intervention package is a feasible way to remotely teach decision making related to online shopping. Decision making is one of the foundational pieces to more complex financial literacy skills. Implications for future research and limitations of the study are also discussed. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]