Objective: To systematically review definitions of functional abdominal pain orders (FAPDs) and outcome measures used in therapeutic randomized controlled trials in pediatric FAPDs adhering to the Outcome Measures in Rheumatology recommendations. Study design: Cochrane, MEDLINE, Embase, and Cinahl databases were systematically searched from inception to April 2018. English-written therapeutic randomized controlled trials concerning FAPDs in children aged 4-18 years were included. Definitions of FAPDs, interventions, outcome measures, measurement instruments, and outcome assessors of each study were tabulated descriptively. Quality was assessed using the Delphi List. Results: A total of 4771 articles were found, of which 64 articles were included (n = 25, 39% of high methodologic quality). The Rome III (50%), Rome II (17%), Apley (16%), and author-defined (17%) criteria were used to define FAPDs. Fourteen studies (22%) assessed a pharmacologic, 25 (39%) a dietary, and 25 (39%) a psychosocial intervention. Forty-four studies (69%) predefined their primary outcomes. In total, 211 reported predefined outcome measures were grouped into 23 different outcome domains; the majority being patient-reported (n = 27, 61%). Of the 14 studies that evaluated a pharmacologic intervention, 12 (86%) reported on adverse events. Conclusions: Studies on pediatric FAPDs are of limited methodologic quality and show large heterogeneity and inconsistency in defining FAPDs and outcome measures used. Development of a core outcome set is needed to make comparison between intervention studies possible.