To assess the long-term effects of tadalafil, a therapeutic agent for fetal growth restriction (FGR), we evaluated the developmental progress of 1.5-year-old infants whose mothers had taken tadalafil during pregnancy. Twenty-four infants were assessed. We evaluated infant body weight, height, and head circumference, and performed the Kyoto Scale of Psychological Development (KSPD) test, a standardized developmental assessment covering Postural–Motor (P–M), Cognitive–Adaptive (C–A), and Language-Social (L–S) functions. The sum score was converted to a developmental quotient (DQ). The mean gestational week of the included cases was 36.1 (29–39) weeks, and the mean birth weight was 1841 (874–2646) g. Twenty-one and 20 out of the 24 cases, respectively, attained body weight and height similar to those of age-matched normal infants (within the 3rd percentile); all cases caught up in head circumference. KSPD was performed for 18 cases at 1.5 years of corrected age. The mean DQ scores were 87 (in total): 82 in P–M, 90 in C–A, and 88 in L–S. The total DQ score in one case (5.6%) was less than 70, and ranged from 70 to 85 in five cases (27.7%), and was more than 85 in 11 cases (61.1%). The growth and development of infants born of tadalafil-treated mothers seem to show good progress at a corrected age of 1.5 years.