This chapter reports a systematic review of the Mexican literature around transition to school published over the first quarter of the twenty-first Century. It examines the complexities of this transition in light of ever-changing Mexican educational policies, diverse but rich cultural traditions, a vibrant linguistic diversity, and extreme socio-economic inequalities. Making preschool education mandatory at the beginning of the millennium placed Mexico as a world leader in recognising the relevance of this educational level. However, the mandatory nature of preschool education and curricula alignment do not seem to have yielded the expected outcomes given the prevailing low enrolment rates and limited emphasis on policies to promote a smooth transition. The effectiveness of government policies is overshadowed by a constant shift in educational policies every time a new president leads the country. Mexican transition research is confined to limited and isolated studies, with no large-scale and longitudinal studies. This limits our knowledge and understanding of the transition. Mexico’s severe social inequalities make this transition challenging for rural and indigenous populations. Holistic transition policies and programs, collaborative school-family partnerships, targeted support for vulnerable groups, and more research are urgently needed in Mexico. Implications for research and practice are discussed.