The relative age effect (RAE) has been demonstrated in many youth and professional sports. In this study, we hypothesized that there would also be a RAE among youth chess players who are typically involved in a complex cognitive task without significant physical requirements. While typical RAEs have been observed in adult chess players, in this paper we wanted to focus primarily on youth chess players. In addition, we also examined RAEs in both participation rates and performance levels in a national chess championship. Therefore, the RAE was examined in a complex cognitive task that has no significant physical requirements, more specifically among youth chess players. Data were analyzed (1) for all registered Belgian youth chess players over a 5-year period (2009-2013) and (2) for participants of the Belgian youth championship 2013. Results indicated an overall RAE among all Belgian youth chess players over the last 5 years. The likelihood of participation was significantly greater for players born in the first birth-date quartile (?[superscript 2] = 10.21, p < 0.05; r = -0.77, p < 0.01; w = 0.07) and the likelihood of participation decreased when youth chess players were born in the last quartile of the year. These effects were most prominent in the under-8 and under-10 year olds. There also appeared to be a performance-related RAE. Kolmogorov-Smirnov tests (p < 0.05) showed that players born in the first months of the selection year were significantly more often in the top 10 players for each age level of the "Belgian" Youth Championship 2013.