As digital technologies continue to evolve, the significance of user experience (UX) in determining the success of software and services has become increasingly apparent. The User Experience Questionnaire Plus (UEQ+) serves as a versatile tool designed to assess UX through questionnaires that are specifically tailored to address unique challenges. Within this context, a critical yet frequently overlooked factor is Trust. Trust encompasses a user’s confidence in a software’s ability to perform reliably, maintain security, and respect user data privacy, and is particularly crucial in sectors such as financial services, health informatics, and e-commerce platforms. This paper details the development and validation of Trust as a novel factor within the UEQ+. The initial phase of this work involved assembling a preliminary set of potential items to define the trust factor. A rigorous study with 405 participants then enabled the refinement of these items to four essential elements through a structured factor analysis approach. Subsequent stages encompassed three distinct phases of validation, engaging a total of 1497 participants, during which these items underwent thorough validation. This extensive process culminated in the establishment of a robustly validated factor, Trust, comprised of the following key items: insecure-secure, untrustworthy-trustworthy, unreliable-reliable, and non-transparent-transparent.