Visuospatial working memory (VSWM) is essential to human cognitive abilities and is associated with important life outcomes such as academic performance. Recently, a number of reliable measures of VSWM have been developed to help understand psychological processes and for practical use in education. We sought to extend this work using Item Response Theory (IRT) and Computerised Adaptive Testing (CAT) frameworks to construct, calibrate and validate a new adaptive, computerised, and open-source VSWM test. We aimed to overcome the limitations of previous instruments and provide researchers with a valid and freely available VSWM measurement tool. The Jack and Jill (JaJ) VSWM task was constructed using explanatory item response modelling of data from a sample of the general adult population (Study 1, N = 244) in the UK and US. Subsequently, a static version of the task was tested for validity and reliability using a sample of adults from the UK and Australia (Study 2, N = 148) and a sample of Russian adolescents (Study 3, N = 263). Finally, the adaptive version of the JaJ task was implemented on the basis of the underlying IRT model and evaluated with another sample of Russian adolescents (Study 4, N = 239). JaJ showed sufficient internal consistency and concurrent validity as indicated by significant and substantial correlations with established measures of working memory, spatial ability, non-verbal intelligence, and academic achievement. The findings suggest that JaJ is an efficient and reliable measure of VSWM from adolescent to adult age.