Existing Australian measures of racist attitudes focus on single groups or have not been validated across the lifespan. To redress this, the present research aimed to develop and validate a measure of racial, ethnic, cultural and religious acceptance--the Australian Racism, Acceptance, and Cultural-Ethnocentrism Scale (RACES)--for use with children, adolescents and adults. Interviews and focus groups were conducted with 30 adolescents in Victoria, Australia, to develop the instrument, which was pilot tested with eight children. The novel 34-item scale consists of three subscales (Accepting Attitudes--12 items; Racist Attitudes--8 items; Ethnocentric Attitudes--4 items) and a 10-item measure of social desirability. The instrument was tested with 296 Victorian school children, 182 adolescents and 120 adults from the Australian community, with data modelled and analysed utilising classical test theory and item response theory. Estimates of internal consistency reliability and factorial, construct, convergent and discriminant validity support the measure. The instrument is the first general attitudinal measure of racial, ethnic, cultural and religious acceptance to be designed and scientifically validated within the Australian context. RACES can be utilised across the lifespan to evaluate attitudes towards all racial, ethnic, cultural and religious groups. RACES has potential to be widely utilised to evaluate anti-racism and pro-diversity interventions implemented within schools and throughout the community, enabling the development of a strong evidence base for initiatives to reduce community levels of racism. However, future research is needed to confirm the psychometric properties and establish the temporal stability of the scale prior to dissemination throughout Australia.