Background <p>Chikungunya virus (CHIKV) causes acute febrile illness with severe arthralgia; management is largely supportive and corticosteroid use remains controversial. We evaluated whether early, short-course, low-dose dexamethasone was associated with shorter acute symptom duration during the 2019 Bangkok outbreak.</p> Methods <p>We retrospectively analyzed 187 adults with confirmed CHIKV and severe arthralgia. Thirty-nine received dexamethasone 4&#xa0;mg/day for 3 days within ≤ 48&#xa0;h of symptom onset plus standard care; 148 received standard care alone. Primary outcomes were duration of the acute febrile phase and duration of rheumatic manifestations abstracted from records and patient reports. Secondary outcomes included C-reactive protein (CRP) and adverse events. Follow-up laboratory tests occurred at clinician discretion and were summarized in early (days 3–5) and late (days 6–8) windows.</p> Results <p>The dexamethasone group had shorter acute febrile phase (median 3 vs. 5 days, <i>p</i> &lt; 0.001) and rheumatic manifestations (7 vs. 10 days, <i>p</i> &lt; 0.001). At late follow-up, median CRP was lower (20 vs. 35&#xa0;mg/L, <i>p</i> &lt; 0.001). Adverse events were uncommon and similar (gastrointestinal discomfort 5% vs. 3%, <i>p</i> = 0.45).</p> Conclusions <p>In this retrospective cohort, early, short-course, low-dose dexamethasone was associated with shorter acute symptom duration and lower inflammatory markers without an observed increase in adverse events. Randomized trials are warranted to determine efficacy, safety, and generalizability.</p> Clinical trial <p>This study was registered with the Thai Clinical Trials Registry (TCTR20201022004) on 22 October 2020.</p>