Objective The Lewy body dementias (LBD, dementia with Lewy bodies and Parkinson's disease dementia) are the second most common cause of neurodegenerative dementia but remain under‐recognised, with long delays from initial assessment to diagnosis. Whilst validated instruments have been developed for key symptoms, there is no brief instrument for overall diagnostic assessment suitable for routine practice. We here report the development of such assessment toolkits. Methods We developed the LBD assessment toolkits in three stages. First, we conducted a systematic search for brief validated assessments for key symptoms and combined these into draft instruments. Second, we obtained feedback on acceptability and feasibility through two rounds of interviews with our patient and public involvement group. This led to modification of the toolkits. Finally, we piloted the toolkits in a feasibility study in routine dementia and Parkinson's disease services to produce final instruments suitable for routine clinical practice. Results Eleven clinicians, working in both dementia/memory assessment and Parkinson's disease/movement disorder services, consented to pilot the assessment toolkits and provide feedback on their feasibility. Clinicians worked in routine health service (not academic) settings and piloted the draft toolkits by integrating them into their regular clinical assessments. Feedback obtained informally, by written comments and through qualitative interviews led to modifications and production of final acceptable versions. Conclusions We were able to address an important need, the under‐diagnosis of LBD, by developing toolkits for improving the recognition and diagnosis of the LBD, which were acceptable to clinicians working in routine dementia and Parkinson's disease services. © 2016 The Authors. International Journal of Geriatric Psychiatry Published by John Wiley & Sons, Ltd.