Despite increased investment in early childhood care and education (ECCE) globally, little is known about its effectiveness in low-income countries. Using kernel exact matching within a national sample of 1,623 Zambian 6-year-olds, we test the associations between ECCE participation and seven domains of children's school readiness. We find ECCE participation to be significantly and positively predictive of children's receptive vocabulary, letter naming, reasoning, fine motor, executive function, and task performance skills (d = 0.20 − 0.65). Although ECCE predicted better outcomes across program types and dosage levels, associations between ECCE participation and school readiness were descriptively if not significantly larger for children attending nonprofit (versus governmental or private) programs and for those attending ECCE between three and five hours per day (versus those attending less than three or six or more hours per day). Implications of these findings, particularly for the 68% of Zambian children who remain out of ECCE, are discussed.