The font size effect is a metamemory illusion in which larger-font items produce higher judgments of learning (JOLs) but not better memory, relative to smaller-font items. We conducted meta-analyses to determine what is currently known about how font size affects JOLs and memory accuracy. In addition, we implemented both univariate and multivariate meta-regressions to isolate the moderators of JOL effects and memory effects. The results revealed a small-to-moderate effect of font size on JOLs. There was also a small but significant effect of font size on memory. This suggests that JOLs and memory accuracy both increase with font size, rather than being completely dissociated. Moreover, JOL-memory dissociation only occurred when font size ranged between very small and intermediate. Our working explanation is that the memory effects of font size are tied to (dis)fluency, but its JOL effects are not. Some boundary conditions were identified for font size effects on both JOLs and memory. Specifically, larger font sizes only reliably increased both JOLs and memory accuracy (a) when font sizes ranged from intermediate to very large, (b) when study materials were unrelated word lists, (c) when JOLs were solicited immediately after encoding, and (d) when study time was relatively brief.