Background <p>The aim of this study was to investigate the effects of conventional suture (CS) and modified sling suture (MSS) techniques, applied in free gingival graft (FGG) surgery using gingival unit graft (GUT) and conventional graft (CG) techniques, on clinical parameters and graft dimensions.</p> Methods <p>52 individuals having Cairo Type 2 (RT2) and Type 3 (RT3) gingival recessions in mandibular anterior were divided into four groups as (a) GUT + MSS (<i>n</i> = 13), (b) GUT + CS (<i>n</i> = 13), (c) CG + MSS (<i>n</i> = 13) and (d) CG + CS (<i>n</i> = 13). Keratinized tissue width (KTW), relative gingival recession height (rGRH), and relative vestibule depth (rVD) measurements were recorded using a digital caliper and UNC 15 periodontal probe. Dimensional changes (Δ) of the graft surface area (GSA) was determined by ImageJ software. All measurements were done at baseline, 1st and 3rd months.</p> Results <p>It was determined that the increase in KTW in the 1st and 3rd months in GUT + CS group was significantly higher than GUT + MSS group (<i>p</i> &lt; 0.05). There was no statistically significant difference in Δ rVD and Δ rGRH values between the groups. When ΔGSA (mm2) values were compared between the groups, the decrease in the 1st and 3rd months in the CG + MSS group was found to be significantly higher than the GUT + MSS and GUT + CS groups (<i>p</i> &lt; 0.05).</p> Conclusion <p>Within the limits of this study, it can be concluded that keratinized tissue can be obtained successfully with both GUT or CG techniques in FGG surgery, on the other hand, regardless of the suture technique, GUT showed less graft shrinkage than CG.</p> Trial registration <p>The study was retrospectively registered at ClinicalTrials (Registration number: NCT06197893; Date of registration: 11 January 2024).</p>