The aim of this systematic review and meta-analysis was to identify and evaluate the effects of individual characteristics associated with mathematical word problem-solving skills among elementary school-aged children and to unpack the quality of studies investigating these associations. The systematic review was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and records were obtained through five electronic databases and citation searching. Study quality was assessed by using the National Heart, Lung, and Blood Institute (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. The meta-analysis (139 reports and 1480 effect sizes) showed that students' overall mathematics achievement (r = 0.56), specific components of mathematics (e.g., calculation; r's = 0.41 to 0.52), basic mathematical processes (e.g., number naming; r's = 0.42 to 0.54), general cognitive skills (e.g., listening comprehension; r's = 0.30 to 0.58), and maths-related affective factors (e.g., motivation; r's = 0.22 to 0.33) were associated with mathematical word problem-solving. By and large, these associations did not depend on study quality (e.g., concerning aims, participants, predictors and outcomes). However, to ensure generalisable, replicable and reliable results in future studies, promoting the study quality related to participants, predictors and outcomes is warranted. These findings provide a comprehensive understanding of various individual characteristics related to mathematical word problem-solving and the quality of studies investigating such associations.