Objective Conduct a systematic review of pediatric randomized controlled trials (RCTs) published in high-impact journals to assess the reporting of primary outcomes and the psychometric properties of their measures. Study Design and Setting Systematic review with screening and simultaneous data extraction conducted by two independent reviewers. Electronic searches of six general medicine and four pediatric journals were conducted in MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL) databases. RCTs of a single phase/step in a single publication, published in English between 2000 and 2010 with participants less than 21 years of age were included. Results A random sample of 20% (n = 445) of 2,229 initial references was screened and 206 (46%) met inclusion criteria. Half (48.5%) of included studies reported a singular primary outcome, 27% did not identify any primary outcome, and 24% identified multiple primary outcomes (range 2–20). Twenty-one trials used an instrument to measure their primary outcome, but only 7 (33%) reported its psychometric properties. Conclusion Pediatric trials published in top medical journals have inadequate reporting of their primary outcomes and the psychometric properties of their outcome measures. Whether the issue is one of poor reporting and/or poor validation will be further investigated.