<p>Existing research on the associations among self-concept clarity, player-avatar identification, and Internet gaming disorder has largely relied on cross-sectional designs, and the findings were inconsistent. This three-wave longitudinal study examined whether self-concept clarity and player-avatar identification jointly and reciprocally relate to Internet gaming disorder symptoms among emerging adults using both general and random-intercept cross-lagged panel model. Participants were 877 role-playing gamers (<i>M</i>_<i>age</i> = 19.81, <i>SD</i>_<i>age</i> = 1.33; 54.80% female) with a baseline and two follow-up surveys (at six and twelve months). Results of both general and random-intercept cross-lagged panel models indicated that, contrary to the hypotheses, self-concept clarity did not predict Internet gaming disorder symptoms nor vice versa, and neither self-concept clarity nor player-avatar identification showed significant indirect effects on Internet gaming disorder symptoms. Although player-avatar identification maintained a positive association with Internet gaming disorder symptoms at the between-person level, it showed no prospective effects at the within-person level. The present study did not provide empirical support for any hypothesized prospective mechanisms among the measured variables. Still, its findings suggest that domain-specific cognitive factors, such as player-avatar identification, may be informative for monitoring Internet gaming disorder risk and highlight the need to support self-concept development during emerging adulthood.</p>