Background This in vitro study evaluated monomer release from different light-cured composites used for clear aligner attachments over time, assessing the effects of composite type, attachment size and curing duration.Methods Four composite materials (3M™ Filtek™ Supreme Flowable, 3M™ Filtek™ Z350 XT Universal, 3M™ Transbond™ XT, and Tokuyama Estelite Posterior) were shaped into attachment-like specimens using 3D-printed molds with heights of 3 mm, 4 mm, and 5 mm. Polymerization was performed using a VALO LED curing unit with two curing protocols (6 s and 12 s). Monomer release was quantified at 1 hour, 1 day, 7 days, and 14 days using high-performance liquid chromatography (HPLC). Statistical analyses were performed using Kruskal–Wallis and post-hoc Bonferroni tests (p < 0.05).Results Intragroup analyses demonstrated significant height- and time-dependent differences in TEGDMA and Bis-GMA release for all composites under both curing protocols (p < 0.001). Under 6 s curing, monomer release increased with specimen height, whereas 12 s curing reduced early elution and yielded more stable profiles. Intergroup comparisons revealed significant differences among composites at all heights, curing durations, and time points (mostly p < 0.001).Conclusion Light-curing duration, attachment size, and composite type significantly influence monomer release.