The study aim was examining the effect of a program based on Cloud-computing platform on developing assessment strategies for EFL primary school teachers. The study reviewed the literature and previous studies dealing with assessment strategies (self-assessment, peer-assessment, strategic use of Questioning and reflection), professional learning communities, cloud computing and finally some platforms for assessment (Google Classroom, Kahoot, Quizizz, Quizlet, Wordwall, Padlet). The researcher prepared a list of assessment strategies and cloud-computing platforms as guides for the design of the instruments. The researcher also designed a pre/post assessment strategies test, a questionnaire, and a rubric, to obtain data for developing the trainees' performance, the researcher designed the proposed program. Then, after a Facebook announcement, the researcher nominated the Egyptian primary teachers (n=25) who intended to study the online assessment course for developing their assessment strategies. These participants were submitted to a pre and posttest. The scores were analyzed both quantitatively and qualitatively. Results showed that the cloud-computing platform was highly effective in developing the assessment strategies for EFL primary school teachers.