Background and Objectives: Anemia and stunting are major public health concerns for young Indonesian children. Limited information is available from studies on multi-micronutrient supplements in Indonesia. The objective of this study was to investigate the effect of 12-month multi-micronutrient powder (MNP) supplementation on serum hemoglobin levels, anemia, and growth. Methods: A randomized double-blinded placebo-controlled study was performed, including 232 eligible children aged 8-10 months old. Children with severe anemia or stunting/those classed as underweight were not included as subjects. The study was performed in a low-socioeconomic-status community in Jakarta. With an active-to-placebo ratio of 60:40, 139 subjects received MNP sachets twice/day, and 93 subjects received placebo sachets, mixed with complementary food. The outcome parameters were hemoglobin level, anemia, and growth indicators. Per-protocol analysis was performed for 179 (intervention: 110; control: 69) subjects. Results: There were no differences at baseline between the groups, except for the weight-for-length z-scores (WLZ). Upon intervention, the serum hemoglobin level and anemia proportion did not change significantly within the group, and no significant differences were found between the groups (p > 0.05). However, subgroup analysis of non-anemic children at baseline showed a significant increase in hemoglobin levels in the youngest age group (8.0-8.9 months old) receiving MNP compared to placebo (0.13 vs. -0.79, p = 0.031). Iron deficiency anemia proportion showed a similar upward trend upon intervention in both groups. No significant differences in growth were found between both groups. Conclusions: This study failed to find a significant effect of 12-month MNP supplementation on serum hemoglobin level, anemia, and growth.