BACKGROUND: Understanding and measuring implementation processes is a key challenge for implementation researchers. This study draws on Normalization Process Theory (NPT) to develop an instrument that can be applied to assess, monitor or measure factors likely to affect normalization from the perspective of implementation participants. METHODS: An iterative process of instrument development was undertaken using the following methods: theoretical elaboration, item generation and item reduction (team workshops); item appraisal (QAS-99); cognitive testing with complex intervention teams; theory re-validation with NPT experts; and pilot testing of instrument. RESULTS: We initially generated 112 potential questionnaire items; these were then reduced to 47 through team workshops and item appraisal. No concerns about item wording and construction were raised through the item appraisal process. We undertook three rounds of cognitive interviews with professionals (n = 30) involved in the development, evaluation, delivery or reception of complex interventions. We identified minor issues around wording of some items; universal issues around how to engage with people at different time points in an intervention; and conceptual issues around the types of people for whom the instrument should be designed. We managed these by adding extra items (n = 6) and including a new set of option responses: 'not relevant at this stage', 'not relevant to my role' and 'not relevant to this intervention' and decided to design an instrument explicitly for those people either delivering or receiving an intervention. This version of the instrument had 53 items. Twenty-three people with a good working knowledge of NPT reviewed the items for theoretical drift. Items that displayed a poor alignment with NPT sub-constructs were removed (n = 8) and others revised or combined (n = 6). The final instrument, with 43 items, was successfully piloted with five people, with a 100% completion rate of items. CONCLUSION: The process of moving through cycles of theoretical translation, item generation, cognitive testing, and theoretical (re)validation was essential for maintaining a balance between the theoretical integrity of the NPT concepts and the ease with which intended respondents could answer the questions. The final instrument could be easily understood and completed, while retaining theoretical validity. NoMAD represents a measure that can be used to understand implementation participants' experiences. It is intended as a measure that can be used alongside instruments that measure other dimensions of implementation activity, such as implementation fidelity, adoption, and readiness.