Aim: Develop two psychometrically sound questionnaires to assess users' and relatives' opinions of Person‐Centred Care. Evaluate the convergence between the perspectives of the different agents involved in Person‐Centred Care in the older people: Users, relatives and staff. Examine the relationships between Person‐Centred Care and care quality and the users' perceived psychological well‐being. Design: We used the psychometric technology involved in the development and analysis of tests for the first objective. For the second and third objectives, we used a descriptive‐correlational design. Method: The sample comprised 636 clients of older people care residences, 742 relatives and 844 healthcare professionals. The mean age of the centre residents was 81.62 years old (SD = 9.51), the mean age of relatives was 56.7 (SD = 10.15) and the mean age of healthcare professionals was 39.94 (SD = 10.56). Data collection lasted 10 months, between May 2017 and March 2018. Two new Person‐Centred Care instruments were developed and the correlations between different agents were calculated. Results: The newly developed measurement instruments demonstrated a unidimensional structure and high internal consistency and stability over time (users: α =.96, ω =.96, r =.91; relatives: α =.97, ω =.97, r =.95). There was high convergence between the Person‐Centred Care evaluations from the staff, users and relatives, with correlations ranging between.62 and.76. Conclusion: The new measurement instruments were reliable and valid. The opinions of the staff, users and relatives about Person‐Centred Care in the residential centres were in good agreement. Furthermore, Person‐Centred Care was associated with care quality and residents' psychological well‐being. Impact: A gap in the literature is an examination of the extent to which assessments of Person‐Centred Care made by staff agree with those by users of the services and their relatives. In order to do that, two new measuring instruments were developed, which showed excellent psychometric properties, and are able to reliably, validly evaluate Person‐Centred Care.