BACKGROUND: Pediatric multisystem inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS) remains an enigmatic disease process, with phenotypic similarities to Kawasaki disease, although many patients present with transient cardiac dysfunction. Biomarkers help validate diagnosis, but the correlation of biomarkers to disease severity or prognosis is poorly understood. DESIGN: We retrospectively reviewed PIMS-TS patients treated in Oxford between May 2020 and May 2022. Data on demographics, presenting features, biochemical markers, treatment, and outcomes were reviewed, and patients with/without the need for vasoactive medications were compared. RESULTS: We identified 63 patients, median age 10.3 years (range 1.2-15.2 years). Where tested, 51/54 (94.4%) were SARS-CoV-2-antibody positive. Admissions followed regional peaks in SARS-CoV-2 infection. Forty children (63.5%) required vasoactive medications. Amongst those requiring vasoactive medications, peak NT-pro-BNP (median 11,363 ng/L vs. 3741 ng/L, p = 0.004) and length of stay (median 8.4 vs. 6.4 days, p = 0.021) were greater. Vitamin D levels inversely correlated with peak CRP (spearman r = -0.34, p = 0.007) and duration of vasoactive medications (spearman r = -0.34, p = 0.030). Furthermore, low serum vitamin D correlated with lower SARS-CoV-2 anti-nucleocapsid titers (spearman r = 0.43, p = 0.0014). Children receiving IV methylprednisolone, 54/63 (85.7%) (of whom, 16/54 received IVIg and methylprednisolone) had a more rapid fall in CRP than those given IVIg alone (7/63; 11.1%) or no immunomodulatory treatment (2/63; 3.2%). No patients had coronary artery aneurysm or persistent cardiac sequelae at discharge. CONCLUSIONS: Methylprednisolone suppressed CRP early and without evidence of coronary aneurysm in this cohort. We demonstrate a relationship between vitamin D, SARS-CoV-2 anti-nucleocapsid antibody production, inflammatory biomarkers, and duration of vasoactive medication, requiring further validation.