Background <p>Although the Incremental Shuttle Walk Test (ISWT) is commonly used in clinical and research settings, data on its reliability and measurement error indices remain insufficient.</p> Aims <p>To investigate the test–retest and inter-rater reliability of the ISWT in healthy university students and to establish reference values for measurement error indices.</p> Methods <p>Forty-nine participants were recruited, of whom 45 completed all testing procedures. Each participant performed four ISWTs—two administered by Rater 1 and two by Rater 2—across two sessions conducted 2–7 days apart. Test–retest and inter-rater reliability were assessed using intraclass correlation coefficients (ICC), standard error of measurement (SEM), minimal detectable change at the 95% confidence level (MDC₉₅), and Bland–Altman analyses.</p> Results <p>The mean ISWT distance was 638.44 ± 103.50 m and 646.67 ± 109.44 m for Rater 1 across sessions (p=0.255), and 621.11 ± 123.33 m and 654.00 ± 142.53 m for Rater 2 (<i>p</i> &lt; 0.001). Test–retest reliability was good to excellent, with ICCs of 0.899 for Rater 1 and 0.873 for Rater 2. Corresponding SEM and MDC₉₅ values were 33.83 m/93.71 m and 47.43 m/131.39 m, respectively. Inter-rater reliability was also good to excellent, with ICCs of 0.869 in Session 1 and 0.899 in Session 2. Bland–Altman analyses confirmed acceptable agreement.</p> Conclusions <p>The ISWT demonstrated good to excellent test–retest and inter-rater reliability, providing novel reference values for measurement error indices. These findings support its use as a reliable tool for assessing functional exercise capacity in both clinical and research settings.</p> Clinical trial registration <p>ClinicalTrials.gov (Identifier: NCT06638281).</p>