Users’ modifications to electronic nicotine delivery systems (ENDS) products could increase initiation, inhibit cessation, or change the toxicity of the product. This study aims to begin to identify consumers’ common ENDS modification behaviors. We conducted audio-recorded, in-depth one-on-one interviews with 13 adult ENDS users in the metropolitan Atlanta area, who self-reported extensive modification experience. Modifications to coils, batteries, and e-liquids were commonly mentioned. Participants indicated that users modified devices to produce large clouds, change levels of nicotine delivery, alter tastes of e-liquids, and experience different throat hits. Because manufacturers have changed product characteristics to be in line with consumer preferences, interviewees indicated that fewer users currently engage in modifications to coils and batteries compared to the more widespread practice a few years ago. Hobbyists continue to perform modifications and many users continue to misuse or abuse e-liquids, despite the view that fewer users currently alter their ENDS than in the past. The Food and Drug Administration (FDA) regulatory actions that limit certain product characteristics may unintentionally increase the likelihood that users will once again make more extensive modifications to their products, and this should be considered as part of the FDA’s regulatory decision-making process.