This study compares the clinical outcomes of Er,Cr:YSGG (2,780 nm) laser-assisted open-flap (OF) and flapless (FL) esthetic crown lengthening (ECL) for the treatment of altered passive eruption. Thirty-six healthy patients requiring ECL were randomly divided into two groups: OF and FL. Gingivectomy and ostectomy were performed with an Er,Cr:YSGG laser in both groups. The periodontal condition and gingival margin level (GML) were assessed at baseline, immediately postsurgery, and at 1, 3, and 9 months postsurgery. The effect of periodontal phenotype and tooth location on GML and supracrestal gingival tissue dimension were evaluated. A significant difference was detected in the mean of GML at all time points, except between 3 and 9 months. The main tissue rebound after 9 months was 0.25 ± 0.3 mm in the OF group and 0.26 ± 0.3 mm in the FL group (no significant difference) and was significantly higher in thick periodontal phenotypes. Er,Cr:YSGG laser-assisted ECL is a predictable technique that achieved similar outcomes using flap and flapless approaches, providing esthetic and restorative opportunities for clinicians.