Background: The Strengths and Difficulties Questionnaire (SDQ) has been widely used as a brief behavioral screening. The aim of this study was to examine the internal consistency and test-retest reliability of the 3- to 4-year-old version of the SDQ (SDQ 3-4) in Japanese preschool children.Methods: The SDQ 3-4 was administered to 754 parents who had 4- to 6-year-old children attending kindergartens or childcare centers in Wako City, Japan, at 2 different times (Time 1 and Time 2) over a 2-week interval between June and July 2012. Cronbach’s alpha and correlation coefficients were used to examine internal consistency and test-retest reliability, respectively.Results: Of 393 parents who returned their responses at Time 1 (response rate 52.1%), 383 were used for analysis after excluding 10 responses with missing data. Their children’s mean age was 4.7 (standard deviation 0.7) years. The internal consistency (Cronbach’s alpha) was good for the total difficulties score (0.74) and the prosocial behavior scale (0.70). However, it was slightly worse for the emotional symptoms, conduct problems, and hyperactivity scales (0.61-0.66) and poor for the peer problems scale (0.45). Of the 383 included respondents at Time 1, 211 parents returned their responses at Time 2 (response rate: 55.1%). Test-retest reliability (correlation coefficients) was good (0.73-0.82), except for the peer problems scale (0.58).Conclusions: The results support the reliability of the SDQ 3-4 being satisfactory for the total difficulties score and prosocial behavior scale and being acceptable for the emotional symptoms, conduct problems, and hyperactivity scales in Japanese preschool children aged 4-6 years.