Preschool age is a critical developmental period in which motor coordination, sensory processing, and adaptive responses become increasingly refined and support learning, independence, play, and participation in daily activities. Appropriate stimulation may strengthen developmental achievement and children’s responses to environmental demands. Complementary massage therapy has been considered a non-pharmacological stimulation that provides tactile, proprioceptive, and relaxation-related input. This study examined changes in motor and sensory development following complementary massage therapy among children aged 4–6 years. A quantitative quasi-experimental one-group pretest-posttest study was conducted at TK Aisyiyah Bustanul Athfal (ABA) Batangtoru, North Sumatra, Indonesia. Forty preschool children completed all stages of the study. Motor and sensory development were assessed before and after a structured complementary massage intervention using the same outcome measures. Paired-samples t tests were used to compare pretest and posttest scores, while Cohen’s dz was calculated to estimate effect size. The mean motor development score increased from 68.13 (SD = 4.76) to 82.50 (SD = 7.16), with a mean increase of 14.38 points, t(39) = 11.01, p < .001, Cohen’s dz = 1.74. Sensory development increased from 63.13 (SD = 4.03) to 81.13 (SD = 4.46), with a mean increase of 18.00 points, t(39) = 21.06, p < .001, Cohen’s dz = 3.33. These findings indicate statistically significant and large improvements in both outcomes. Complementary massage may serve as supportive developmental stimulation when delivered safely by trained personnel and integrated with age-appropriate educational activities. However, the absence of a control group limits causal interpretation. Future studies should use controlled multisite designs, validated assessment instruments, larger samples, and longer follow-up periods. These approaches are needed to determine whether observed improvements persist over time and represent clinically meaningful benefits for children.