Anxiety and depressive disorders are common and continue to increase in prevalence. However, most individuals who meet the criteria for these disorders do not receive any treatment, and only a small portion receive evidence-based care. Digital mental health interventions (DMHIs) are one way to increase access to evidence-based psychological treatments. Evidence supports the efficacy of disorder-specific and transdiagnostic DMHIs based on cognitive-behavioral therapy for anxiety and depression. Most of these interventions focus on reducing symptoms and negative affect. However, research indicates that deficits in positive affect, a related yet distinct construct, are common across these disorders. The current study reports on the development of an Internet-based version of the unified protocol that also targets positive affect regulation. We also report results from a small initial pilot study (N = 4) on the acceptability of the intervention, preliminary outcomes, and participant feedback used to inform refinements to the program. Participants generally found the program to be acceptable. In terms of preliminary outcomes, there was a statistically significant reduction in anxiety symptoms at the group level from pre- to posttreatment. There were no other statistically significant results at the group level from pre- to posttreatment on stress, depression, savoring, or well-being. However, individual participants reported clinically significant changes in various outcomes. Results also highlight the importance of receiving participant feedback early in the development process.